Ergonomic cup handle design analysis at Naruna Ceramic Studio: A literature review

Abstract

This study aims to determine the dimensions of the cup handle that are more comfortable for the user. The manufacture of cup handles generally does not involve dimensions with special standards but instead follows the shape of the cup itself. A unique design is not enough for a better user experience. Comfort must be considered using anthropometric dimensions and biomechanical strength. It is known the hand grip position has greater biomechanical strength than the lateral pinch grip position and can be used as a reference for determining the right dimensions for designing ergonomic cup handles. To achieve a hand grip position, it is necessary to change the shape of the cup handle with anthropometric measurements, it is known that the cup handle, which can fit the user’s four fingers, has a dimension of 73.70 mm. However, the characteristics of the clay will make the ceramic experience shrinkage in dimensions. A dimensional tolerance of 21% is given so that anthropometric measurements can be achieved so that the handle dimension that can be proposed is 89.17 mm. It is hoped that the dimensional changes in the cup handle will be a consideration for future studies and designs.

Keywords:

• hand grip
• ergonomics
• anthropometry
• biomechanics
• cups
• ceramics
• cup handles

1. Introduction

Ergonomics is a multidisciplinary science that focuses on human activity. This science can be classified based on how the product will meet human needs. Product ergonomics meets human comfort parameters, while process ergonomics focuses on the production methods used in producing products (Davies et al., 1980; McCormick et al., 1987; Sekulová et al., 2015). This multidisciplinary science can extend to various fields of human activity and must function according to human needs.

Human activity can consist of various hand movements such as grasping, lifting, pushing, pulling, holding, grabbing, and stabilizing. The most common movement involving the function of the hands is grasping activity (Figure 1). Grasping activity can be in the form of grasping movements with different postures and positions. In the power grip position (Figure 1) (Pheasant & Haslegrave, 2006) the hand position grips the product perfectly and involves interaction between all the finger joints. Meanwhile, in the precision grip position (Figure 1) (Pheasant & Haslegrave, 2006), the gripping activity is only carried out by two to three fingers. The difference in gripping posture, of course, also affects the grip’s strength and the hand’s comfort when carrying out the movement. Hand grips are an important component in simple activities because they are often used to interact with one or more objects in everyday life (Lee & Jung, 2015).

Figure 1. Various grasping activities (Pheasant & Haslegrave, 2006).

Pain can reduce grip strength. That’s why, a comfortable handle design needs to be designed to support grip activity. In supporting comfort to support these activities so that they are comfortable, biomechanical aspects are needed. This aspect can be used to identify the strength of the grip created by the angle of the finger joints and differences in muscle length (Buchholz & Armstrong, 1991). The dimensions of the product being held can be a factor in posture changes that can improve the biomechanical aspects of gripping activities. Because the hilt involves the interaction of the fingers that form the gripping posture, the size of the human body needs to be further studied to reduce the problems caused by the grip.

Information about the size of the human body can be found in anthropometric data which can support the design process for better product designs and following the user (Saengchaiya & Bunterngchit, 2004). In designing cup handles, teapot handles, pot handles, door handles, and various products with other handle parts that are ergonomic, it is necessary to have dimensions related to the hands to support activities. However, in this study, the handle in question is a ceramic cup handle. Hand anthropometric measurements can be categorized as anatomical measurements with functional measurement variables related to hand movement, hand span, finger flexion and extension, and the position of wrist abduction or adduction (Garrett, 1971; Greiner, 1991).

A unique and elegant design alone is not enough to provide a better user experience. Cutlery such as unique and elegant coffee cups (Figure 3) will elevate the image and complement the food served. However, a unique and elegant design alone is not enough to provide a better user experience. Ergonomic aspects need to be considered so that users are satisfied with the beautiful design and can feel comfortable using the cutlery. Thus, a better dining experience will be achieved by using appropriate cutlery (Nazri et al., 2022).

The manufacture of cup handles generally does not involve dimensions with specific standards but rather follows the shape of the cup itself, as has been shown in several local ceramic industries (Doulton Indonesia, Tangerang, Banten; Nuansa Porcelain Indonesia, Boyolali, Central Java; Naruna Ceramic Studio, Salatiga; Sango Ceramics Indonesia, Wonosari, Semarang). The handle of a ceramic cup is made by forming an elongated cylinder using clay material which is then bent and attached to the side of the cup (Figure 2). The results of this formation produce products with less consistent dimensions because there are no standard dimensions that can be used as a reference in the formation of the handle of the cup. In determining the ergonomic dimensions of cup handle length, an anthropometric approach is needed to determine dimensions based on the limbs involved in the activity. The data can be in the length, width, and diameter of the finger components and can be measured using calipers, tape measure, and finger circumference measurement (Garrett, 1971). A common cup design can accommodate two of the user’s fingers with the other two supporting from the outside of the grip (Pitelka, 2001). When viewed from an anthropometric aspect, the two fingers’ width dimensions have a length of 40.00 mm (Çakıt et al., 2014). Meanwhile, an ergonomic handle design should not be less than 100.00 mm (Government of Canada, 2023). The dimensions of the body size will then be used in determining the ergonomic cup handle. A good design does not only have the right dimensions, but must be located in the right position. The handle of the good side of a cup should not be located far from the center of gravity of the cup (Hedge, 2013).

Figure 2. Cup handle formation.

The ceramic craftsman will choose a suitable soil to make workpieces, especially clay that is still wet and has plastic properties needed to model the desired shape. The clay that has been formed will then be dried, causing it to lose the water element in it so that the plastic properties of the material will disappear (Boch & Niepce, 2007). Therefore, the addition of geometric tolerances as a result of the nature of clay which always shrinks after drying and hardening, is also required at the manufacturing stage of ceramic products. Ceramics have characteristics where their components experience shrinkage in dimensions after combustion. The percentage of burnt shrinkage can be measured to anticipate the dimensional deformation of processed ceramics. Dimensional changes in ceramics depend on the ceramic type and the burning duration at a certain temperature. In alumina ceramics (Rana et al., 2009) the dimensional shrinkage is experienced by 11.30% at a firing temperature of 1650oC.

Meanwhile, in stoneware ceramics, fired ceramics at high temperatures of 1200 – 1300oC experience a dry shrinkage of 7–8% and a burnt shrinkage of 8–10% (Solichin, 2012). This is why the dimensions of the cup handle, when it is still in the form of clay, will shrink after the clay is dried and then fired at high temperatures. So that in the stage of design, manufacture, and fabrication of ceramic products requires consideration from the ergonomic aspect, and technical aspects related to determining size tolerances based on material properties are also needed so that the product results match the desired dimensions when implemented on the production floor. However, up to this decade, it is still rare to find research related to geometric tolerances and shapes of ceramic component handles for cups, mugs and glass products.

This study will comprehensively explain the determination of the dimensions of ceramic cup handles based on Indonesian anthropometric measurements. This study was conducted in a local ceramics industry that was successful in carrying out various innovations in unique colored porcelain ceramic products, but the shape and geometry of the handle still need to be evaluated for product development related to the dimensions of the handle that are more comfortable according to standard anthropometric measurements. Therefore, an ergonomic analysis related to the anthropometry of human hands as potential users of ceramic cup products is used by researchers to solve cases experienced by the local ceramics industry.

Previous researcher different material like bone china cup plate-type ceramic waste powder was utilized as a fine aggregate (Gautam et al., 2022); effect of ceramic waste on physical, chemical, mechanical, and durability properties (Gautam et al., 2021), bone-china ceramic powder waste (BCPW) and granite cutting waste (Gautam et al., 2023), bone china ceramic waste (BCCW) in self-compacting concrete (SCC) as a partial substitution for cement (Gautam et al., 2022), bone-china ceramic powder waste (BCPW) and granite waste (GW) (Gautam et al., 2022), bone china ceramic waste powder (BCCWP) obtained from broken or distorted bone china ceramic waste products, and the second is granite cutting waste (GCW) from the granite cutting and shaping industry (Gautam et al., 2022),

2. Materials and methods

This study was conducted based on reputed research article published by several researchers.³ The intended paper is a paper that has been published in English containing the terms “Ergonomics”, “Hand Function”, “Hand Biomechanics”, “Hand Anthropometry”, and “Ceramic Tableware” which can be found in the title, abstract, or keywords.

2.1. Biomechanical’s posture

In the biomechanical aspect, the existence of postural efforts will be associated with the occurrence of static muscle contractions (Chaffín et al., 1982). Postural efforts occur due to tension in the muscles that last for a long time. The discomfort in this posture will compress the blood vessels and inhibit blood flow to the muscles so that the muscles that are burdened will experience a decrease in the supply of sugar and oxygen when lactic acid and carbon dioxide accumulate, creating muscle fatigue which can lead to cramps (Chaffín et al., 1982).

The difference in the posture that is not good will hinder the experience of using the product, so excessive effort in maintaining an uncomfortable posture will result in prolonged pain. Pain can reduce grip strength. Differences in gripping posture will affect grip strength and hand comfort when making movements. The hand grip is an important component in simple movements because it is often used to interact with one or more objects in everyday life (Lee & Jung, 2015)⁴.

Grasping activity can be in the form of grasping movements with different postures and positions. In the power grip position (Figure 1) (Pienimaki et al., 2002; Pheasant & Haslegrave, 2006) the hand position grips the product perfectly and involves interaction between all the finger joints. Meanwhile, in the precision grip position (Figure 1) (Pheasant & Haslegrave, 2006), the gripping activity is only carried out by two to three fingers. The difference in gripping posture also results in differences in the strength of the grips used. Postures that do not provide the ability to grip more firmly will potentially cause interference with the ability to manipulate object in movements (Lee & Jung, 2015). Object manipulation in movements shows the ability of the limbs to move in moving objects from one place to another.

If the Object manipulation in movements ability is weak, it will have an impact on other activities that also involve hand skills. Therefore, it is necessary to measure hand strength based on these different postures to be able to compare the possible effect of posture on increasing the strength of gripping activities. In this study, measurements of hand grip strength were measured according to the hand grip posture of male and female Turkish dental students. The data has been shown to be normal and tested using the Kolmogorov-Smirnov test at the 5% level of significance (Çakıt et al., 2014). Measurements for grip strength and pinch strength were carried out using a digital handgrip dynamometer and a mechanical pinch gauge to see the difference in strength from the two different grip postures.

In using cup products, grasping activity is an important movement because it relates to how to operate the product. That’s why, a comfortable handle design needs to be designed to support grip activity. In supporting comfort to support these activities so that they are comfortable, biomechanical aspects are needed.

2.2. Anthropometric measurements

The design of work equipment and products that provide comfort and safety when used is the hope of every user. As for achieving this goal, a design must be adjusted to user needs in order to increase the value of the product. Ergonomic design of equipment and products can enable a product to provide comfort and safety when used. Ergonomic design is carried out to achieve the goal of comfort for users who carry out activities using the product. This comfort can be achieved if the product used is in accordance with the user’s body dimensions (Chaffín et al., 1982).

Anthropometry is the measurement of the human body which comes from the word “anthropos” which means human and “metron” which means measurement. Thus, anthropometry can be defined as a study that involves measuring the dimensions of the human body (Bridger, 2003). Anthropometry is very closely related to the dimensions and characteristics of the human body consisting of weight, volume, center of gravity, as well as the properties of inertia in the body and muscle strength (Tayyari & Smith, 2003).

Measurements using anthropometry can be carried out by involving body measurements and can be used as a reference in designing products related to the human body (Van Wilgen et al., 2003). As for knowing the dimensions of the user’s body, equipment and products that are designed according to the dimensions of the human body can create comfort for users when using products and ensure the health and safety of users when using them. Therefore, it is necessary to consider anthropometric aspects in designing ergonomic products in order to achieve the goal of user comfort.

Cup designs that generally accommodate one to two fingers can cause discomfort for prolonged use (Buchholz & Armstrong, 1991). In order to create user comfort when using the product, consideration through anthropometric aspects needs to be done. Anthropometric dimensions can be measured by measuring the limbs that are directly involved in product use activities. In ceramic cup products, the limbs that interact directly with the product components are the hands, especially the fingers that will grip the ceramic cup handle. When gripping, the fingers pass through the empty space between the cup body and the handle (Figure 8). The number of fingers that pass through the cup handle will determine the level of comfort that the user can feel. This shows that the cup handle’s dimensions will determine the user’s comfort when using the cup. Thus, it is possible to decide on standard dimensions for cup handles so that fingers can pass through the space between the cup and cup handles to find ergonomic cup handle dimensions.

If the handle component causes the hand to pass through the hole (in this case the cup handle) then the recommended allowance is 115 mm of thumb mesh length (Pheasant & Haslegrave, 2006). This dimension is also in accordance with the standard tool design by the Canadian Center for Occupational Health and Safety (CCOHS) that the recommended handle length dimension for a hand tool is around 120 mm (Government of Canada, 2023).

In determining the ergonomic dimensions of cup handle length, an anthropometric approach is needed to determine dimensions based on the limbs involved in the activity. The data can be in the form of length, width, and diameter of the finger components and can be measured using calipers, tape measure, and finger circumference measurement (Garrett, 1971). There are 33 anthropometric data that have been measured according to the parts of the hands of male and female Turkish dental students. The data is normal and tested using the Kolmogorov-Smirnov test at the 5% significance level (Çakıt et al., 2014). A comparison of the strength of the grip that can contain one finger with the design can then be tested using a biomechanical approach. Grip strength measurement based on the fingers involved was carried out to determine the ratio of the resulting strength. A digital handgrip dynamometer and a mechanical pinch gauge were measured for grip strength and pinch strength. This measurement was carried out on male and female students from the Faculty of Dentistry in Turkey, referring to a previous study conducted by Cukurova University (Çakıt et al., 2014). In this measurement, participants are positioned in a sitting position with their arms parallel to the body and the floor. The strength test used to measure hand grip strength, lateral pinch strength, and chuck pinch strength can also be compared with populations in India (Fernandez & Uppugonduri, 1992), South India (Mandahawi et al., 2008), Jordan (Mathiowetz et al., 1985), America (Mathiowetz et al., 1985), England, Malaysia, and Israel (Çakıt et al., 2014).

2.3. Sample characterization

Traditional ceramics are divided into several categories (Figure 3) based on their function and examples of their application on the production floor (Pfeifer, 2009). Cement, like concrete and mortar, is a type of traditional ceramic that is a mixture of synthetic minerals consisting of four main compounds, namely tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. Cement is generally used in constructing roads, bridges and buildings because of its hard nature and bonds through hydration reactions at ambient temperatures that do not require heat.

Figure 3. Categories of traditional ceramics.

The next type is refractory ceramic, generally used as thermal insulation in high-temperature furnaces. Refractory materials generally consist of silica, aluminum silicate, and magnesite which resist degradation due to corrosive gases or liquids and are able to withstand solids at high temperatures (Pfeifer, 2009).

The next application of ceramics is in glass, generally in the form of mirrors, windows, containers, and lighting fixtures, almost entirely made of silica with additives such as other oxidizing agents. Structural clay products such as bricks, tiles, and pipes are also examples of ceramic applications in the industrial world. The product originates from the combination of silica and alumina with a number of other oxides such as magnesia, titania, potassium oxide and sodium oxide.

The types of ceramics that are the focus of this study are whiteware ceramic products such as stoneware which includes tableware, artware, tiles, porcelain, and cookware. These products use compounds that are almost the same as other types of ceramics and have different material characteristics according to their function and type (Pfeifer, 2009).

Before it can reach its condition as a solid ceramic, stoneware ceramic will acquire plastic properties when the clay comes into contact with water which makes the surface wet. This plasticity will then make it easier for ceramic craftsmen to process workpieces into the desired shapes. To be able to achieve a solid state, the clay must lose the water element contained in it so that the plastic properties can be lost. Drying and heating processes can be carried out and the allowable heating rate for the material depends on the thermal expansion of the material (Green, 2007). Changes in volume and shrinkage of product size will result from compaction that occurs during the heating process. The combustion temperature depends on the composition and desired properties of the final product (Green, 2007).

Based on the properties of ceramics which can experience shrinkage after the firing process, measurement of the percentage of burnt shrinkage can be carried out to anticipate the dimensional deformation of processed ceramics. Dimensional changes in ceramics depend on the ceramic type and the burning duration at a certain temperature. In alumina ceramics (Rana et al., 2009), the dimensional shrinkage is experienced by 11.3% at a firing temperature of 1650oC. Meanwhile, in stoneware ceramics, fired ceramics at high temperatures of 1200 – 1300oC experience a dry shrinkage of 7–8% and a burnt shrinkage of 8–10% (Solichin, 2012; Sundari & Supriyadi, 2013).

2.3.1 Dry shrinkage

The change in the characteristics of wet clay to dry is a form of shrinkage better known as dry shrinkage. Shrinkage can occur by 5–8% during drying (Tussniari et al., 2018). Dry shrinkage can be calculated through Equation (1)(1) $\mathit{Dry}\mathit{Shrinkage}\left(S_k\right)=\frac{\left(\mathit{a}-\mathit{b}\right)}{a}\mathit{x}100\mathrm{\%}$(1) .

(1) $\mathit{Dry}\mathit{Shrinkage}\left(S_k\right)=\frac{\left(\mathit{a}-\mathit{b}\right)}{a}\mathit{x}100\mathrm{\%}$(1)

Where a is the plastic length of the ceramic and b is the length of the dry ceramic constant (1).

2.3.2 Burn shrink

The losses experienced as a result of combustion can be called burn losses. This shrinkage can occur due to changes in the chemical and physical properties of the ceramic produced by the combustion process and can be calculated using Equation (2)(2) $\mathit{Burn}\mathit{Shrink}\left(S_b\right)=\frac{\left(\mathit{b}-\mathit{c}\right)}{b}\mathit{x}100\mathrm{\%}$(2) .

(2) $\mathit{Burn}\mathit{Shrink}\left(S_b\right)=\frac{\left(\mathit{b}-\mathit{c}\right)}{b}\mathit{x}100\mathrm{\%}$(2)

Where b is the constant dry ceramic length and c is the ceramic length after firing (2).

3. Result and discussions

The manufacture of cup handles generally does not involve dimensions with special standards but rather follows the shape of the cup itself. The handle of a ceramic cup is made by forming an elongated cylinder using clay material which is then bent and attached to the side of the cup. The results of this formation produce products with less consistent dimensions because there are no standard dimensions that can be used as a reference in the formation of the handle of the cup.

In fulfilling the aesthetic aspect, making unique cup handles is needed so that there are several variations in the shape of the cup handles that can provide added value to the product design of the ceramic cup. In the ceramic cup model (Figure 4) it is known that for a cup size with a volume of 220 ml, a ceramic cup generally has a height dimension of 8.50 cm and a diameter of 8.00 cm. These dimensions correspond to the standard IKEA Mug (IKEA 365+ mug - 8 oz dimensions & drawings (no date) RSS, 2023) which measures 8 oz with dimensions of a cup height of about 7.00 cm and a cup diameter of 8.00 cm. There are no specific dimensions for forming cup handles, but the sizes of cup handles range from sizes that one finger and two fingers can fit through. Aesthetic aspects can be fulfilled, but comfort aspects also need to be considered in order to add functional value to ceramic cups (Figure 5).

Figure 4. Ceramic cup : (a) model 1; (b) model 2; (c) model 3.

Figure 5. IKEA 365 mug 8 oz.

In using cup products, grasping activity is an important movement because it relates to how to operate the product. That’s why, a comfortable handle design needs to be designed to support grip activity. In supporting comfort to support these activities so that they are comfortable, biomechanical aspects are needed.

The handle of a good cup should not be larger than the shape of the cup so that it can fit the fingers that will grip the handle. The right dimensions will not make the fingers move farther from the center of gravity that is owned by the cup so that the grip becomes stable. Dimensions that are too large will make it difficult for the fingers to support the cup and the grip becomes unstable due to the free movement of the fingers. However, a handle dimension that is too small will make the pressure on the fingers more concentrated and uneven. The smaller the amount of tissue on the surface of the skin that is pressed against the cup handle, the more uncomfortable the grip will be.

Therefore, a new cup handle dimension design is carried out which combines the dimensions of the width of the second joint from the index finger to the little finger. Extending the dimensions of the cup handle is done with the hope that the user can achieve a maximum grip position so that the use of the cup can be more comfortable and improve the quality of the user experience when using it. Extending the dimensions of the cup handle also means increasing the area the handle is likely to come into contact with the skin surface. The greater the amount of tissue on the surface that is pressed against the cup handle, the more comfortable the grip will be because there is pressure that is more even and not concentrated on just one finger.

The minimum dimensions of the cup handle will cause discomfort to the user when using the cup for a long duration and have the potential to cause interference with the ability of object manipulation in movements (Lee & Jung, 2015; Nordenskiold & Grimby, 1997). Object manipulation in movements shows the limbs’ ability to move objects from one place to another. If the Object manipulation in movement ability is weak, it will impact other activities that also involve hand skills. In this study, the ability to grip a cup. This is shown through the results of grip strength measurements (Table 1), which show that the biomechanical strength for the hand grip is greater than the lateral pinch strength created by using a cup handle with minimum dimensions.

Table 1. Definition of measurement of Biomechanics (Çakıt et al., 2014)

Biomechanics	Measurement Definition
Hand grip strength (kg)	The shoulder is adducted and neutrally rotated, the elbow flexed to 90 degrees, and the forearm and wrist is in a neutral position.
Lateral pinch strength (kg)	The maximum force generated by a person squeezing between the tips of the thumb and index finger
Chuck pinch strength (kg)	Thumb pad to pads of the index and middle fingers

Figure 6(a) shows the lateral position of the pinch grip, which is the force that is formed due to the interaction in the form of a pressing position played by the tip of the thumb with the index finger. This position describes the position of the fingers on the cup handle in general, which can only contain one finger. Meanwhile, Figure 6(b) indicates a hand grip position or perfect gripping position which will cause the shoulders to stretch 90 degrees and the wrists to be in a normal position. The two positions cause differences in biomechanical strength, which is measured in kilograms (kg). Based on the data obtained from Table 2, it is known that the hand grip position has an average biomechanical strength of 41.37 kg for male hand strength and 26.32 kg for female hand strength. Meanwhile, in the lateral pinch grip position, the biomechanical strength of the male hand is 6.19 kg, and that of the female is 4.50 kg.

Figure 6. (a) lateral pinch grip; (b) hand grip.

Table 2. Grip strength measurement results (Çakıt et al., 2014)

Biomechanics Measurement	Males (n = 92)				Females (n = 73)
	Right Hand		Left Hand		Right Hand		Left Hand
	5th	95th	5th	95th	5th	95th	5th	95th
Hand grip strength (kg)	31.10	53.92	29.23	51.24	21.01	34.61	18.28	31.38
Lateral pinch strength (kg)	3.50	8.55	3.71	9.00	2.50	7.00	2.00	6.50
Chuck pinch strength (kg)	5.00	11.50	5.00	11.66	3.11	8.66	3.33	8.38

Both of these values are still lower than the measurement results of the hand grip position, so it can be seen that the hand grip position has greater biomechanical strength and can be used as a reference for determining the right dimensions for designing ergonomic cup handles (Figure 7). In order to achieve a hand grip position, it is necessary to change the shape of the cup handle which originally could only fit one finger to be able to accommodate a maximum of 4 fingers of the user’s hand. This is done so that the loading of the cup is not centered on one finger but is evenly distributed on the surface of each finger. As for getting the dimensions of this position, it is necessary to do an analysis in terms of anthropometry relating to the fingers of the human hand. When gripping, the fingers pass through the empty space between the cup body and handle (Figure 8). The number of fingers that pass through the cup handle will also determine the level of comfort that the user can feel. This shows that the cup handle’s dimensions will determine the user’s comfort when using the cup. Thus, it is possible to determine standard sizes for cup handles so that fingers can pass through the space between the cup and cup handles to find ergonomic cup handle dimensions.

Figure 8. 2D model cup handle reference.

Figure 7. Hand measurement and hand depth diagram (Çakıt et al., 2014).

The anthropometric data used to measure the ergonomic dimensions of the cup handle are the width dimensions of the joints of the two fingers. The data were obtained from the measurement results of male and female dental students in Turkey (Table 3). The width of the joint of the two fingers (Figure 8) is used as a reference in determining the long dimension of the cup handle because when using a cup, the part of the finger that can pass through the hole of the cup handle is only limited to the second joint. This can be shown in Figure 8. which shows the part of the finger that is able to pass through the handle of the cup.

Table 3. Results of measurement of hand dimensions from male and female Turkis Dentistry students (Çakıt et al., 2014)

Hand Dimension	Males (n = 92)				Females (n = 73)
	Right Hand		Left Hand		Right Hand		Left Hand
	5th	95th	5th	95th	5th	95th	5th	95th
(12) Breadth at the second joint of digit 2	17.40	21.23	16.85	20.41	15.25	19.21	14.79	17.33
(13) Breadth at the second joint of digit 3	17.72	20.96	17.09	20.46	15.60	17.93	15.03	17.27
(14) Breadth at the second joint of digit 4	16.39	19.63	16.13	19.40	14.46	17.84	14.18	16.50
(15) Breadth at the second joint of digit 5	14.50	17.66	13.89	17.33	12.23	16.99	12.26	14.63

In general, cup handles are only able to contain one finger so when using the dimensions reference in Table 3, the dimensions that can be used as a reference are the width dimensions of the joints of the two fingers. So, using data with the 95th percentile with the consideration that the data is able to cover 95% of the body size of a number of populations. Through calculations using 95th percentile data for right and left hand sizes of women and men, it is known that the average handle length of a cup is 19.55 mm. This dimension does not meet the standard of grip comfort based on the ergonomic standard of the handle of a product. In general, when the handle component causes the hand to pass through the hole (in this case the cup handle) then the recommended dimension for the cup handle is 115 mm of thumb mesh length (Pheasant & Haslegrave, 2006). This dimension is also in accordance with the standard tool design by the Canadian Center for Occupational Health and Safety (CCOHS) that the recommended handle length dimension for a hand tool is around 120 mm (Government of Canada, 2023). Thus, it is known that the actual dimensions of the cup handle and the recommended dimensions still have a size difference of 95.45 mm.

When using the dimension references in Table 3, the dimensions that can be used as a reference are the dimensions of the width of the joints of the two fingers (12), the width of the joints of the three fingers (13), the width of the joints of the four fingers (14), and the width of the joints of the five fingers (15) (Figure 9). Using data with the 95th percentile with the consideration that the data can cover 95% of the body size of a number of populations, the average handle length of the proposed cup is 73.70 mm.

Figure 9. 2D model drawing proposed cup handle design.

However, in order to achieve this size, the formation of the handle of the cup must be adjusted to the ability of the clay to shrink after drying and firing. Before it can reach its condition as a solid ceramic, stoneware ceramic will acquire plastic properties when the clay comes into contact with water, making the surface wet. This plasticity will then make it easier for ceramic craftsmen to process workpieces into the desired shapes. To be able to achieve a solid state, the clay must lose the water element contained in it so that the plastic properties can be lost. Drying and heating processes can be carried out and the allowable heating rate for the material depends on the thermal expansion of the material (Green, 2007). Changes in volume and shrinkage of product size will result from compaction that occurs during the heating process. The combustion temperature depends on the composition and desired properties of the final product (Anggoro et al., 2021; Anggoro et al., 2022; Green, 2007).

In stoneware ceramics, fired ceramics at high temperatures of 1200 – 1300oC will experience a dry shrinkage of 7–8% and a burnt shrinkage of 8–10% (Solichin, 2012). Thus, to achieve a cup handle size that is comfortable to use with anthropometric standard sizes, the formation of the dimensions of the clay before it is dried and fired must be accompanied by a dimensional tolerance of 21%. If the dimensions to be achieved are 73.70 mm, then the clay must be shaped with a size of 89.17 mm before being dried and fired to become the handle of a ceramic cup.

The resulting cup handle length dimension of 89.17 mm is still not sufficient for the minimum handle dimension recommendation set by the Canadian Center for Occupational Health and Safety (CCOHS) that the recommended handle length dimension for a hand tool is around 120 mm (Government of Canada, 2023) and recommendations that the dimensions of the cup handle are as far as the thumb netting is 115 mm (Pheasant & Haslegrave, 2006). However, when compared with the data prior to the design evaluation, the resulting dimensions of the cup handle which can fit four fingers, have smaller data deviations than the dimensions of the cup handle which can only contain one finger. The dimensions of the cup handle which can only contain one finger have a data deviation of 95.46 mm with the recommended handle dimension being 115 mm long. While the dimensions of the cup handle after evaluation that four knuckles can pass have a data deviation of 25.83 mm. The dimensions of the cup handle, which can only contain one finger, can fulfill 16.99% of the sizes recommended while the dimensions of the cup handle after evaluation which four knuckles can pass can fulfill 77.54% of the dimensions recommended so that it can be seen that there is an improvement and an expansion of the previous cup handle dimensions.

The cause of the recommended dimensions cannot fully meet the recommended standards because the population data used is data on the dimensions of the hands of medical students in Turkey which must be adjusted again using data on the user population in Indonesia. Therefore, the results of the analysis will be used by the authors to conduct further research and verify the size of the ergonomic cup handle.

This study is an initial study that aims to find the general dimensions of cup handles that suit comfort in terms of ergonomics and biomechanics so that discomfort in use can be minimized. This goal is supported by several previous studies, including research which states that hand grip position has better biomechanical strength than lateral pinch strength (Çakıt et al., 2014) and determining anthropometric dimensions to achieve this hand grip position based on similar research (Çakıt et al., 2014; Nag et al., 2003) as well as the addition of size tolerances based on previous research which describes the material’s ability to shrink after drying and firing processes (Anggoro et al., 2021; Anggoro et al., 2022; Tussniari et al., 2018).

4. Conclusion

This study was conducted to find a more ergonomic cup handle dimension. Based on the results of studies based on various published literature, conclusions can be attained.

1. Data shows that pain elicited by the hand weakens the grip. A cup design that can only fit one to two fingers of the user will cause discomfort for long-term use. The greater the amount of tissue on the surface that is pressed against the cup handle, the more comfortable the grip will be because there is pressure that is more even and not concentrated on just one finger. Therefore, to improve the user experience in using the cup, the anthropometric data obtained is then processed to obtain a more ergonomic cup handle dimension.

2. The results of data analysis show that the appropriate grip size is 73.70 mm. This size covers 95% of the body size of a number of populations. However, due to the characteristics of the material which will shrink after going through the drying and burning stages, the initial dimensions of the clay formation must be accompanied by a tolerance of 21% so that anthropometric dimensions can be achieved. So, the total length of the cup handle that must be formed is 89.17 mm.

3. The resulting cup handle length dimension of 89.17 mm is still not sufficient for the minimum handle dimension recommendation set by the Canadian Center for Occupational Health and Safety (CCOHS) that the recommended handle length dimension for a hand tool is around 120 mm (Government of Canada, 2023) and recommendations that the dimensions of the cup handle are as far as the thumb netting is 115 mm (Pheasant & Haslegrave, 2006). This is because the population data used is data on the dimensions of the hands of medical students in Turkey which must be adjusted again to use user population data in Indonesia in the next study.

4. The increase in the value of the cup handle can be seen from the difference in the strength of the biomechanical aspects of the cup handle which can only fit one finger and the handle which can contain four knuckles. This is supported by grip strength measurement data from the biomechanical aspect which shows that the grip position obtained after evaluating the cup dimensions is larger than the old cup handle design. The hand grip position obtained after extending the size of the cup handle causes the biomechanical strength resulting from the grip to be stronger than the lateral pinch grip position created due to the dimensions of the cup handle being at a minimum size.⁷

The results of this study are expected to be used by designers and engineers working in the ceramics industry to create more ergonomic cup products. As for later this study can also be implemented and used by the author to conduct further research and verify the size of the ergonomic cup handle.

Disclosure statement

No potential conflict of interest was reported by the author(s).