Tell Me About Cups | How Shape, Handles, Ceramics, Glass, Insulation, Drinking and Cup Design Work

Tell me about cups. A cup is a small open container designed mainly for drinking. Cups hold liquids while giving the user a rim, handle or body shape that makes lifting, sipping and pouring predictable. They can be made from ceramic, glass, stainless steel, paper, plastic, silicone or composites, and their geometry affects heat retention, spill resistance, aroma, grip and cleaning.

When people ask how cups work, the central ideas are containment, thermal transfer and human interface. The wall must hold liquid without leaking, the rim must feel comfortable against the lips, and the base must keep the cup stable. Hot-drink cups also need to manage heat flowing toward the hand while allowing enough heat to reach the mouth at a safe and pleasant rate.

Modern cups are therefore compact packaging and tableware systems. A porcelain teacup, double-wall glass, paper takeaway cup, insulated travel mug and reusable plastic cup solve different combinations of temperature, portability, durability and cost. Good cup design balances volume, handle geometry, lid sealing, cleaning, manufacturing and the way aroma and liquid flow reach the drinker.

The 50-Second Answer

A cup contains liquid with walls and a base while the rim controls drinking and pouring. Handles or insulated surfaces keep the hand away from uncomfortable temperatures.

Material, wall thickness and shape determine how fast the drink cools, how stable the cup feels and how easily it can be cleaned.

In practical use, the 50-second answer interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Cup Shape

Most cups are cylinders, tapered vessels or rounded forms because those geometries hold liquid efficiently and are easy to manufacture.

Shape also determines stackability, grip and how smoothly liquid approaches the rim when the cup is tilted.

The trade-off around cup shape often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

The Rim

The rim is the liquid’s final boundary before it reaches the mouth. A smooth rounded rim feels comfortable, while a thin rim can create a precise pouring edge.

Rim diameter also changes the drinker’s nose position and therefore aroma perception.

For diagnosis, examine the physical path involved in the rim: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Rim Thickness

Thin rims feel delicate and release liquid cleanly. Thick rims are stronger and more comfortable on rugged cups.

The right thickness depends on material and intended use; glass and porcelain can use finer lips than moulded fibre or thick plastic.

From a manufacturing perspective, rim thickness has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Cup Diameter

Wide cups expose more liquid surface to air and tend to cool faster.

Narrow cups retain heat somewhat longer and reduce spill risk while walking, but can feel less open during drinking.

In practical use, cup diameter interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Cup Height

Tall cups fit more volume into limited table width.

Height raises the centre of mass and can make a narrow cup easier to tip, especially when nearly full.

The trade-off around cup height often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Taper

Many cups are wider at the top than the bottom. Taper supports nesting and makes mould release easier.

It also changes stability and hand grip, with a narrower base requiring careful proportion.

For diagnosis, examine the physical path involved in taper: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

The Base

A flat or ring-shaped base carries the cup’s weight.

Base diameter matters for tipping resistance, while foot geometry can reduce contact with hot tabletops.

From a manufacturing perspective, the base has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Handles

Handles let the hand lift a hot cup without gripping the body.

Their opening, thickness and attachment points must suit finger size and carry the full cup load safely.

In practical use, handles interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Handle Leverage

The handle places the hand away from the cup’s centre, creating bending load at the attachment points.

Ceramic handles need generous fillets and good firing because sharp corners concentrate stress.

The trade-off around handle leverage often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Handle Openings

Small handles may fit only one or two fingers; larger mug handles support three or four.

Grip style affects comfort and how much torque the wrist must control.

For diagnosis, examine the physical path involved in handle openings: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Handleless Cups

Many tea, coffee and traditional drinking vessels have no handle.

Thin walls, moderate serving temperature or small volume make body gripping practical and culturally familiar.

From a manufacturing perspective, handleless cups has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Ceramic Cups

Ceramic cups are clay-based bodies fired into rigid vessels.

Their moderate thermal conductivity and substantial heat capacity make them well suited to hot drinks.

In practical use, ceramic cups interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Porcelain Cups

Porcelain can be thin, white and strong after high-temperature firing.

Thin walls reduce mass while a smooth vitrified surface resists staining and odour.

The trade-off around porcelain cups often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Stoneware Mugs

Stoneware mugs are usually thicker and heavier than porcelain cups.

They feel substantial, retain heat well and tolerate everyday use, though they can chip at rims and handles.

For diagnosis, examine the physical path involved in stoneware mugs: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Earthenware Cups

Earthenware bodies are lower-fired and more porous beneath glaze.

Good glaze provides a food-safe surface, but chips can expose absorbent clay.

From a manufacturing perspective, earthenware cups has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Glaze

Glaze seals ceramic pores and provides colour and a smooth drinking surface.

Glaze fit must match the body so repeated hot-cold cycles do not create crazing or edge flaking.

In practical use, glaze interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Glass Cups

Glass cups are transparent, non-porous and chemically inert.

They let the drink colour remain visible but can be brittle and conduct heat more rapidly than thick ceramic.

The trade-off around glass cups often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Borosilicate Cups

Borosilicate glass expands less with temperature change.

This improves thermal-shock resistance and supports thin-walled hot-drink cups and double-wall designs.

For diagnosis, examine the physical path involved in borosilicate cups: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Tempered Glass Cups

Tempering places the outer surface into compression.

It improves impact resistance and changes breakage behaviour, though chipped or deeply scratched edges still reduce strength.

From a manufacturing perspective, tempered glass cups has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Double-Wall Glass

Double-wall cups use an inner and outer glass shell separated by an air gap.

The gap reduces heat transfer to the hand and makes the drink appear visually suspended.

In practical use, double-wall glass interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Vacuum Insulation

Insulated stainless cups can evacuate the space between two metal walls.

Removing most gas suppresses conduction and convection, leaving radiation and small solid bridges as main heat paths.

The trade-off around vacuum insulation often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Stainless Steel Cups

Stainless steel is durable, corrosion resistant and nearly unbreakable in ordinary drops.

Single-wall cups transfer heat quickly; double-wall vacuum designs manage temperature far better.

For diagnosis, examine the physical path involved in stainless steel cups: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Travel Mugs

Travel mugs combine insulation with lids, seals and one-handed drinking features.

Their performance depends as much on closure design as on the insulated body.

From a manufacturing perspective, travel mugs has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Lids

A lid reduces splashing and slows heat loss from the top surface.

It also changes aroma release and drinking flow, which is why open-cup and travel-mug experiences feel different.

In practical use, lids interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Sip Openings

Small lid openings meter flow and reduce spill volume during movement.

Too small an opening creates slow drinking and pressure pulses unless air can enter elsewhere.

The trade-off around sip openings often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Vent Holes

Air must enter a lidded cup as liquid leaves.

A separate vent prevents glugging and allows a smoother continuous stream through the sip opening.

For diagnosis, examine the physical path involved in vent holes: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Seals

Silicone or elastomer gaskets close gaps between lid and cup.

Seal compression must be high enough to resist leakage but low enough that the lid remains removable.

From a manufacturing perspective, seals has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Threads

Screw lids convert rotation into axial sealing force.

Thread starts, pitch and stops determine how quickly a lid closes and where the seal lands.

In practical use, threads interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Snap Lids

Disposable cups often use snap-on rims.

The lid bead flexes over a matching cup flange and locks underneath without threads.

The trade-off around snap lids often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Paper Cups

Paper cups use coated paperboard formed into tapered cylinders.

A polymer or aqueous barrier prevents liquid soaking through the fibre structure during the intended use period.

For diagnosis, examine the physical path involved in paper cups: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Cup Sleeves

Cardboard sleeves reduce heat transfer from hot takeaway cups to the hand.

Corrugations and air spaces add insulation without increasing the cup’s own wall thickness.

From a manufacturing perspective, cup sleeves has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Plastic Cups

Disposable and reusable plastic cups use polypropylene, PET, polystyrene or other polymers depending on temperature and clarity needs.

Polymer choice controls stiffness, crack resistance and suitability for hot drinks.

In practical use, plastic cups interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

PET Cold Cups

PET is clear and stiff, making it common for cold beverages.

It is generally not the preferred material for very hot liquids because heat can soften or distort thin forms.

The trade-off around pet cold cups often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Polypropylene Cups

Polypropylene tolerates higher temperatures and repeated washing better than many clear disposable plastics.

It is common in reusable food-service cups and microwave-compatible containers where appropriately rated.

For diagnosis, examine the physical path involved in polypropylene cups: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Silicone Cups

Silicone is flexible, heat resistant and collapsible.

Travel cups use reinforcing rings or lids because flexible walls alone can deform unpredictably when full.

From a manufacturing perspective, silicone cups has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Mugs

A mug is generally larger and more robust than a delicate cup.

Thicker walls and big handles suit coffee, cocoa and everyday use, trading refinement for capacity and durability.

In practical use, mugs interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Teacups

Teacups are often smaller and thinner than mugs.

Their open shapes encourage aroma perception and let hot tea cool toward drinking temperature relatively quickly.

The trade-off around teacups often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Espresso Cups

Espresso cups are small because beverage volume is small.

Thick ceramic can reduce rapid cooling while the narrow capacity keeps crema and aroma concentrated.

For diagnosis, examine the physical path involved in espresso cups: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Cappuccino Cups

Cappuccino cups are wider than espresso cups and hold milk foam.

Bowl-like curvature supports pouring latte art and maintains a balanced coffee-to-milk volume.

From a manufacturing perspective, cappuccino cups has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Saucers

Saucers catch drips and provide a stable place for spoons.

They also create an insulating air gap between a hot cup base and sensitive tabletop surfaces.

In practical use, saucers interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Measuring Cups

Measuring cups include calibrated volume markings.

Accuracy depends on geometry, marking position and reading the liquid meniscus at eye level.

The trade-off around measuring cups often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Meniscus

Liquids curve at container walls because of surface tension and wetting.

For transparent measuring cups, the reading convention uses the appropriate part of the meniscus rather than the visually highest edge.

For diagnosis, examine the physical path involved in meniscus: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Graduations

Volume lines must correspond to actual internal geometry.

Printed or moulded marks need quality control because wall taper means equal vertical spacing does not always equal equal volume increments.

From a manufacturing perspective, graduations has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Pouring Spouts

Some measuring cups include spouts that create a narrow controlled stream.

A sharp lip encourages clean separation and reduces liquid running down the outside wall.

In practical use, pouring spouts interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Heat Capacity

The cup itself absorbs heat from the drink.

A heavy cold mug can noticeably cool a small beverage, while pre-warming reduces this initial loss.

The trade-off around heat capacity often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Conduction

Heat moves through cup walls toward the hand and room.

Material conductivity, wall thickness and contact area determine how rapidly the outside warms.

For diagnosis, examine the physical path involved in conduction: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Convection

Warm cup surfaces heat surrounding air.

Air movement increases convective cooling, which is why a drink cools faster near a fan or open window.

From a manufacturing perspective, convection has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Evaporation

The exposed liquid surface loses heat as water evaporates.

Wide open cups therefore cool faster than narrow lidded vessels, especially in dry moving air.

In practical use, evaporation interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Radiation

Hot cups emit thermal infrared radiation.

Shiny metal surfaces can have lower emissivity than matte ceramics, though the total effect competes with conduction and convection.

The trade-off around radiation often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Pre-Warming

Rinsing a cup with hot water before serving reduces the temperature difference between vessel and drink.

This is especially useful for small coffee servings where the cup mass is large compared with beverage mass.

For diagnosis, examine the physical path involved in pre-warming: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Pre-Chilling

Cold cups slow warming of iced drinks and desserts.

Condensation forms outside if the surface falls below the room-air dew point.

From a manufacturing perspective, pre-chilling has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Condensation

Water droplets on a cold cup come from humid air, not from liquid leaking through the wall.

Double-wall insulated cups keep the outer surface warmer and therefore reduce condensation.

In practical use, condensation interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Aroma

Wide open cups let volatile aroma compounds reach the nose more easily.

Cup shape can therefore influence perceived flavour even when the liquid itself is unchanged.

The trade-off around aroma often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Lip Contact

Rim smoothness and temperature influence drinking comfort.

Very hot metal rims can feel more intense than ceramic because metal transfers heat to the lips quickly.

For diagnosis, examine the physical path involved in lip contact: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Grip Texture

Glossy surfaces can become slippery when wet.

Textured glazes, silicone bands or knurling increase grip without requiring larger handles.

From a manufacturing perspective, grip texture has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

Stacking

Stackable cups use tapered walls and controlled internal stops.

Stops prevent cups wedging so tightly that users damage rims while separating them.

In practical use, stacking interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Dishwasher Use

Reusable cups face hot water, detergent and repeated mechanical handling.

Seals, printed graphics and bonded handles must survive the same cycles as the main body.

The trade-off around dishwasher use often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Staining

Coffee and tea pigments can stain porous surfaces and some plastics.

Glazed ceramic, glass and stainless steel resist staining better because they are less permeable.

For diagnosis, examine the physical path involved in staining: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Odour Retention

Some plastics and silicone absorb aroma compounds from coffee, milk or spices.

Thorough cleaning and full drying reduce retained odour, while glass and stainless steel are generally more neutral.

From a manufacturing perspective, odour retention has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

A Worked Example: Travel Mug Flow

A sealed travel mug has one sip hole and no vent.

As liquid tries to leave, internal pressure drops and flow pulses. Adding a small vent lets air replace the lost volume and creates a smooth stream.

In practical use, a worked example: travel mug flow interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

A Worked Example: Condensation

An iced drink cools a single-wall cup below the room’s dew point.

Water vapour from the air condenses on the outside surface, producing droplets even though the cup wall is perfectly watertight.

The trade-off around a worked example: condensation often involves comfort, insulation, manufacturability and cleaning. Improving one property can make the cup heavier, harder to stack or more expensive, so successful designs balance several needs rather than maximising one number.

Common Misconceptions

A thick cup does not automatically keep drinks hot, double walls do not always contain a vacuum and condensation does not mean the cup leaks.

Cup performance depends on material, geometry, insulation and the lid working as one system.

For diagnosis, examine the physical path involved in common misconceptions: where liquid, heat, force or air actually moves. This reveals whether the problem belongs to the body, rim, lid, seal or user interaction instead of treating every leak or discomfort as one fault.

Choosing a Cup

Choose open ceramic or glass for aroma and table use, vacuum stainless for long temperature retention, reusable polymer for toughness and paper systems for short disposable service.

The best cup depends on drink temperature, portability, cleaning and expected lifetime.

From a manufacturing perspective, choosing a cup has to stay consistent across large production runs. Mould shrinkage, firing variation, coating thickness and assembly tolerances all matter because small dimensional changes can alter fit, sealing, stacking and drinking feel.

The Systems View of Cups

A cup links liquid containment, heat transfer, human grip, lip comfort and manufacturing.

Its simple form succeeds when the drink reaches the user at the right rate and temperature without leaking, tipping or demanding awkward handling.

In practical use, the systems view of cups interacts with temperature, fill level and hand movement. Designers test the complete cup because a feature that works well when empty can behave differently once the vessel is hot, full, lidded or repeatedly washed.

Frequently Asked Questions

Ceramic cups hold heat through thermal mass, glass provides chemical neutrality and visibility, vacuum stainless cups minimise heat transfer, and paper cups rely on barriers and sleeves for short-term hot-drink service.

A handle is useful but not essential. Small cups can be held by their walls when serving temperature, material and cultural design make direct grip comfortable.