Frequently Asked Questions

It is one of the properties of most materials to expand when heated and contract when cooled. These phenomena can cause problems for decorators who ignore the Laws of Physics. The expansion or contraction of materials used in making the mugs can cause problems in a number of ways. One problem is if the ceramic enamel (paint) has a very different coefficient of expansion (α) from the glaze it is being fired onto then it will either be under tension or compression stresses which can cause the design to either crack or chip off. These problems will be reviewed later.

A somewhat bigger problem is the separation of the mug's handle from the body of the mug when subject to a thermal shock. Basically this happens when the mugs are subject to a rapid increase or decrease in temperature (ΔT). The mug body and handle being made of the same material have the same coefficient of expansions (α) but they have very different masses. Thus the body (with the larger mass) reacts slower to a given temperature rise that does the handle (with the lower mass). This is the force that applies the stress to the handle/mug joint. If this joint can not withstand this stress then it will fail. This handle failure can be noticed as cracks in the glaze in the junction area. Sometimes these cracks are not noticed initially but are later discovered by the end user. These cracks in the glaze can lead to a full fracture when additional stress, experienced when used, are applied. Sometimes the stress is severe enough that the glaze and the body both crack and the mug and handle separate.

To be more specific, let's look at an equation for the linear expansion that occurs in solids when subjected to a change in temperature. Basically the change in length (ΔL) in a solid is proportional to the initial length (Lo) and to the change in temperature (ΔT).

Thus: ΔL = a Lo ΔT

Where: a is the coefficient of expansion

: ΔL = Lf - Lo (Final Length less Initial Length)

Let's review how this Law of Physics can cause mug handles to separate from the mug body.

When a mug is subjected to a rise in temperature (ΔT), the lower mass handle heats up faster than the higher mass body. Since the coefficient of expansion (α) and the initial length are equal for the mug and handle then a faster change in temperature (ΔT) will cause a greater change in the length (ΔL) between the handle and body. If this change in length is large enough then the handle/body joint will fail. In order to eliminate the handle separation the difference in the temperature between the body and the handle mug must be reduced. In a lehr or kiln this can be accomplished by slowing the rate of temperature rise.

Slowing the belt speed in a lehr will lower the change in temperature (ΔT) and thus the change in length (ΔL) between the mug body and handle. This difference in length between the mug and body is directly proportional to the difference in temperature between the body and handle and the speed of the belt is directly proportional to the temperature rise. Thus if the belt speed is cut in half then the difference in temperature is also cut in half and the stress is reduced.

It is also important to review your lehr curve to be sure it does not have any sharp rises in temperature.

Besides reducing the change in temperature (between the mug body and handle). There are a number of other factors that can influence handle failure. We will review some of the more obvious ones.

- The Composition of the mug's bisque influences the difference in length of the body and handle when subjected to a given temperature rise. Looking at the equation again:

ΔL = a Lo ΔT

For any given change in temperature (ΔT), different materials will have a different change in length (ΔL) because every material has a unique coefficient of expansion (α). Thus a material with a low coefficient of expansion, such as porcelain, will not have as large a change in length as a material with a higher coefficient of expansion, such as stoneware. It is this difference in change in length that causes the stress between the mug handle and body.

- The shape of the handle also influences the handle failure rate. A Maui Handle will have a much greater failure rate as compared the classic "C" Handle. In a Maui Handle a large portion of the increase in length is concentrated at the handle/body junction. In the "C" Handle very little of the increase in length is at the handle/body joint. The "C" is shaped like a balloon and most of the increase is in the expansion of the "C" instead of concentrated at the joint.

- The length of the handle also influences the handle failure. In the equation ΔL = a Lo ΔT , the ΔL is directly proportional to the initial length (Lo). So a Maui Mug with a handle that is half the length will have a ΔL that is half the original mug.

- The mass of the handle also influences the failure rate. The closer the mass of the handle corresponds to the mass of the body the less the differences in the respective ΔT . So a very thin handle (low mass) is more likely to fail than a thick handle (high mass) under the same temperature rise.

- Repeated cycling can also cause handle failure. Each time a mug is fired it is subjected to the stress at the mug body/handle joint. Every time the mug is subjected to these forces it is weakened. Eventually enough cycling stress will cause a failure.

As a recap. Let's review why some items are more susceptible to handle failure.

- Probably the most susceptible is the Maui Mug. This item has a large handle (large Lo) and because of it's shape most of the forces caused by the ΔL are concentrated at the handle/mug joint.

- Thicker handles will help lower the difference between the ΔLs between the handle and body because of the greater mass (more closely matches mass of body) and also because of the increased strength of the thicker handles.

- Thicker handles will help lower the difference between the ΔLs between the handle and body because of the greater mass (more closely matches mass of body) and also because of the increased strength of the thicker handles.

In conclusion, if you are having handle failures then the easiest solution is to lower the Δ T between the body and the handle. (Slow the belt speed). You can also avoid those items that are the most susceptible to changes in temperature.

A couple of tricks can also help to reduce the difference in temperature changes between the mug handle and bodies. One is to always point the handles toward the charge end of the lehr. This will allow the body (greater mass) to see the temperature prior to the handle (lower mass). Also always try to have a full lehr which tends to minimize some of the temperature variations in the lehr. It is also preferable to try to single fire mugs to minimize the accumulation of stresses caused by the temperature rise differences between the body and handle.

CCIB stands for "China Commodity Inspection Bureaus". It is a network of provincial, municipal and local inspection offices in China that test ceramic items to assure they are in compliance with the current FDA (US Food and Drug Administration) action levels for leachable lead and cadmium.

Chinese factories that are in compliance with the FDA requirements are included on a list of CIQ SA (State Administration of Entry/Exit Inspection and Quarantine of China) certified factories. All certified factories goods are allowed to enter the USA without additional testing for lead or cadmium.

All certified factories are issued a unique CCIB Number and allowed to use the CCIB stickers on their products (number included on sticker). A CCIB sticker must be attached to every shipping carton or retail carton from these factories.

Examples of CCIB Sticker/logo

Marck & Associates buys exclusively from CIQ SA certified factories.

Ceramic is a generic term for a range of products that are made from inorganic, non-metallic materials, usually fired at high temperatures. It includes glass, earthenware, stoneware, porcelain and bone china. The word "ceramics" is from the Greek word "keramos" which means "Pottery".

Earthenware - Is pottery that has been fired at a temperature of around 1100 C. It is not vitrified. It is porous and needs to be glazed in order to be functional.

Stoneware - Is pottery that has been fired at a high enough temperature (1200 to 1300 C) to partially vitrify (melt together and fuse) the material and make it somewhat impervious to liquids. It is usually covered with colored glazes. If you look at the unglazed bottom ring of a stoneware mug you will notice that the body is cream colored as compared to the white body of a porcelain mug.

Porcelain - Is made with kaolin clay. Kaolin is a white clay that retains its white color when fired. It is fired at temperatures in excess of 1300 C and is more fully vitrified than stoneware. Porcelain ware was first made in China; hence it's commonly referred to as CHINA. It is usually covered with a clear glaze, which allows the white body to show. If you look closely at the surface it appears that the white body has a glass coating on top. The unglazed bottom of the mug will show a white body material.

Porcelanous Stoneware - Is stoneware that has a very white clay body. It is covered with a clear glaze or white glaze. It is more vitrified than regular stoneware but not as vitrified as true porcelain. Mugs made with porcelanous stoneware are usually considered to be porcelain mugs.

Bone China - Is a very translucent white china. One of its component ingredients is bone ash (or it's chemical equivalent) which gives bone china it's translucence and stark whiteness. Bone China is usually very thin and if held to a light source it is translucent.

While the definitions listed above are those most commonly used in our industry, for purposes of duty classification the US Customs defines the various types of ceramic items by the amount of absorption each type has. Below is a listing of the definitions from the Harmonized Tariff Schedule of the United States (2002).

(a) The terms "porcelain," "china" and "chinaware" embrace ceramic ware (other than stoneware), whether or not glazed or decorated, having a fired white body (unless artificially colored) which will not absorb more than 0.5 percent of its weight of water and is translucent in thicknesses of several millimeters. The term "stoneware" as used in this note, embraces ceramic ware which contains clay as an essential ingredient, is not commonly white, will absorb not more than 3 percent of its weight of water, and is naturally opaque (except in very thin pieces) even when absorption is less than 0.1 percent.

(b) The term "bone chinaware" embraces chinaware or porcelain the body of which contains 25 percent or more of calcined bone or tricalcium phosphate.

(c) The term "earthenware" embraces ceramic ware, whether or not glazed or decorated, having a fired body which contains clay as an essential ingredient, and will absorb more than 3 percent of its weight of water

(d) The water absorption of a ceramic body shall be determined by ASTM test method designated C373 (except that test specimens may have a minimum weight of 10 g, and may have one large surface glazed).

Ink is a generic term loosely used to refer to the decorating medium for various substrates. For our discussion, inks fall into two catagories, organic, and inorganic. Organic inks are made of non metallic materials that can be broken down or destroyed if exposed to excessive heat , sometimes as little as several hundred degrees Fahrenheit. These would include Epoxy inks and solvent or water based inks for plastics and paper. Inorganic inks are made using combinations of minerals and metal based compounds that generally must be fired at temperatures exceeding 1,000 degrees Fahrenheit for proper maturation. These are usually refered to as glass enamels or ceramic enamels and are used on glass and ceramic substrates where long term durability and adhesion are needed.

Choosing the right decorating ink for a given substrate can mean the difference between making a good finished product or unusable junk. Due to the many variables one may run into in decorating, it is imperative that before running production on a new item, testing of the substrate and proposed ink should be performed to determine if they are compatible and acceptable for the item's intended use. The best sources for finding what inks should be used for a given substrate are the ink manufacturers themselves. They have put in the time to research what works and what doesn't. However, ALWAYS TEST FIRE SEVERAL SAMPLES FIRST in your facility before blindly accepting the ink manufacturer's recommendations. The conditions in your facility may be far different than their laboratory conditions, and your results may vary from theirs. Always follow the ink manufacturer's directions for best results.

ASA Plastic items that we carry are made using Acrylonitrile Styrene Acrylate plastic, or ASA for short. This plastic is used in a wide range of products including automotive and sporting goods because of it's resistance to weathering, UV resistance, impact resistance and high gloss. Based upon testing done for us by NazDar, we can recommend using their 9700 series inks with 10% NB-80 catalyst added. This was shown to give good adhesion and scratch resistance when properly cured. Isopropyl Alcohol is the recommended solvent to wipe off misprints to avoid damaging the plastic surface. NOTE: Misprints must be wiped off quickly to avoid leaving permanently etched ghost images on the plastic.

Polystyrene plastic items that we carry can be decorated using NazDar's System 2 or S2 series inks. As with the ASA plastics, any misprints should be wiped off quickly with Isopropyl Alcohol to prevent the ink from etching into the surface and ruining the piece.

Our Santa Barbara™ "Satin Finish" tumblers are made with a polyurethane material with a non-slip grip, soft feel texture. NazDar recommends their DA series ink or the 9600 ink series with 10% NB-80 added. It is highly recommended you test in your facility for ink adhesion prior to production.

Polycarbonate plastic water bottles that we carry can be decorated using NazDar's 9600 series inks with 10% NB-80 Adhesion Promoter. Sericol Tech Mark series ink, Poly Plast ink, and Plastijet XG inks may also work well. While many inks may appear to adhere well to the dry plastic, when filled with ice cooled liquids, the bottles will sweat and this may cause the ink to lift from the bottle's surface. We suggest testing your inks to simulate this scenario to avoid nasty surprises later.

Stainless Steel items may be printed with epoxy or other specifically formulated inks. It should be noted, due to the manufacturing process, there may be small amounts of residual oils on the surface that could prevent proper adhesion. Any contamination on the metal surface must be removed prior to decorating, regardless of the ink used, in order to obtain good results. Care must also be used when curing any inks on stainless items, as some double walled items with plastic inner liners and metal outer shells, usually have a foam sealant material between the inner and outer walls. If these double walled items are heated to excess in order to cure the ink decoration, the foam sealant may expand, forcing the plastic liner to separate from the steel shell. Additionally, excess heat may cause the plastic liner, handle, or foam bottom pad to be damaged. We recommend the use of air dry epoxy inks for this particular application.

Glass and Ceramic ware can be decorated using either organic or inorganic ink systems depending upon the desired end use. Organic inks (generally catylized epoxies) have been used where permanence and long term durability is not needed. Otherwise, Inorganic Ceramic Enamels requiring high temperature firing are the ink of choice for permanent, durable decorations on glass and ceramic. The enamel used must properly match the substrate's expansion characteristics and safe firing range to avoid problems during firing and later use. If the ceramic enamel (paint) has a very different coefficient of expansion from the glaze it is being fired onto, then it will either be under tension or compression stresses which can cause the design to either crack or chip off. This "crazing" or "spalling" of the decoration is often run into when "glass firing" enamels are used on porcelain ware. The differences in coeffecients of expansion between these two materials is often enough to cause the cracking or even popping off of the decoration, sometimes even pulling some of the underlying glaze with it. When using epoxy inks or one of the true metallic decorating inks such as gold, platinum/palladium, or copper on glass or ceramics, remove any and all dust from the ware before printing. Failure to clean the surface can result in trapped dust in the epoxy that will show through or leave voids, while dust can cause poor edge definition and/or voids in metallic prints. Ware should also be free of Lubricity spray if using epoxy or metallic golds, etc. Lubricity spray, if not removed before decorating, may cause lack of adhesion with epoxy inks, and discoloration and/or poor adhesion with fired metallic inks.

It should be noted that there are many ink manufacturers and ink systems available that might work well for the items we sell, and it is up to the individual decorators to research what inks are best for their specific applications. In summary, regardless of the substrate, care must be taken to choose a suitable ink system for the item being decorated. The items must be free of contaminants that may prevent good adhesion between the ink and substrate. Always follow the ink manufacturers' recommendations when mixing and using inks. Always test any new inks and substrates prior to production to ensure their suitability for your end use of the finished product.

Depending upon the type of decorating being done, the color of the glaze on a ceramic piece can in some instances affect the decorating process. For example, laser engravers have found that some colors of mugs engrave easier than others. This is likely due in part to the different light absorbing characteristics of the various colored pigments used in the glazes. Some glazes are also softer or harder than others due to the materials used when making glazes for specific purposes. One example is Porcelain glazes. They are harder and have a lower coefficient of expansion than the glazes used on stoneware. This may make engraving or sand blasting more difficult on porcelain than on stoneware. These characteristics would also require matching the properties of the decorating enamels to the glaze for good firing. Some items may be made using multiple glazes that may affect the way the can be safely decorated. Examples of this multiple glaze is our white in, red or orange out ceramic items like the 1168-02/50, 1122-02/96, etc.

In the manufacturing of the Red and Orange overglazed items, the colored glazes are applied over the white glazed piece and then fired. To maintain the bright hues of the red and orange colors, it is necessary to fire these overglaze colors at lower temperatures than would ordinarily be used. Due to the nature of the materials and the process, the red and orange glazes that are applied over the white are softer than the underlying glaze. Because of this, engravers might find the red and orange colors may be cut or blasted a little easier than some other colors. Because of the two layers of glaze on the outside surface, as one cuts or blasts into the surface of the ware, depending upon how deep they cut, they will get either white from the underlying glaze or the bisque showing through. If the ware is to be screen printed or decaled and then fired, care must be taken to fire as slow as possible and at the lowest safe firing temperature (glass firing range) to minimize problems that might arise from differences in the coefficient of expansion of the three materials (white body, colored glaze, and decoration).

Due to all the variables involved in decorating, including glazes and clays used in the ceramics, variations in ceramic enamel composition, thickness of decoration, different firing equipment and firing cycles, etc., we strongly recommend tests be performed prior to actual production runs. Additionally, decorators should work with their decal and color suppliers to be sure there is proper fit between the decoration and the ceramic ware's glaze.

We do not recommend our plastic products for use in dishwashers or microwave ovens. While many of our products might be usable in either appliance, misuse could cause damage to the plastic piece or the appliance or personal injury. For instance, the 7012 plastic shots with stainless steel bottoms or other plastic items with metal trim, if used in a microwave oven, might damage the microwave oven. Additionally, if used in the microwave, any metal trim could become hot enough to melt the plastic and might cause severe burns to anyone handling it. Metal objects should not be used in a microwave oven! Dishwashers, with their high heat, may eventually cause the metal base to separate from the plastic because of the different expansion characteristics of the metal and plastic. Repeated cycles in a dishwasher may also attack screen printed decorations on the plastic over time. To avoid these potential problems we recommend hand washing with a soft dish cloth and mild dish soap.

The numbers "18/8" found on the bottom of many Stainless Steel items stands for the percentage of Chrome and Nickel metals in the Stainless Steel used to make that piece. In this case, the composition of the metal would be:

74% Steel - (For Strength)
18% Chrome - (For Stain Resistance)
8% Nickel - (For Luster).

The California state government in 1986 passed legislation that is intended to warn consumers in the state of the possibility of exposure to toxic chemicals. Officially known as the Safe Drinking Water and Toxic Enforcement Act of 1986, it is better known by its original name of Proposition 65.

Proposition 65 requires the State to publish a list of chemicals known to cause cancer, birth defects, or other reproductive harm. Currently, there are around 750 chemicals listed, with lead and cadmium being the chemicals of concern to decorators.

Proposition 65 requires businesses to notify Californians about significant amounts of these listed chemicals in the products they purchase, in their homes or workplaces, or that are released into the environment. Proposition 65 specifically lays out the required testing method, limits for lead and cadmium leaching, and the warning requirements for articles that exceed the limits.

Limits for warning purposes are covered in the following document: Heavy Metal Limits

Ceramic ware does not need warnings if the leaching test results are below the specified levels shown above. It should be noted that while ceramic dinnerware can exceed these limits and still be legally sold in California, if these limits are met or exceeded, Proposition 65 requires warnings be provided to inform consumers of the potential exposure to the toxic chemicals. In addition, Federal limits still apply to ceramic dinnerware regarding allowable lead and cadmium leaching.

The information provided here is a very brief overview of Proposition 65, and is not meant to answer all questions regarding this law. Any decorators whose products may end up in California (even if not originally sold there), need to be aware of this law, and its ramifications for them, to avoid potential costly problems.

To review the warning requirements, or to view the regulation in its entirety, please refer to the California Office of Environmental Health Hazard Assessment web site at www.oehha.ca.gov/prop65/background/index.html

Liquid capacities (as well as dimensions) given for drinkware are approximate because of small variations from piece to piece due to limitations in the manufacturing processes. Capacities are measured with the liquid full to the brim.

The Federal Trade Commission (FTC) is charged with preventing deception and unfairness in the marketplace. To this end, the FTC has published guidelines for what products can be legally claimed to be "Made in USA".

To learn more about this subject, simply click on the following link to go directly to the FTC's web site dealing with this topic. http://www.ftc.gov/bcp/edu/pubs/business/adv/bus03.shtm

Many of our articles are imported. The requirements of 19 U.S.C. 1304 and 19 CFR part 134 provide that the articles or their containers must be marked in a conspicuous place as legibly, indelibly and permanently as the nature of the article or container will permit, in such a manner as to indicate to an ultimate purchaser in the U.S., the English name of the country of origin of the article. If you remove the country of origin marking from these items, or remove them from the properly marked containers (cartons) in your processing or repacking, you must remark to show the country of origin.

To find out more about marking/labeling requirements for imported goods, you can check out the U.S. Customs publication 0000-0539 on the internet at http://www.access.gpo.gov/nara/cfr/waisidx_05/19cfr134_05.html

U.S. Customs and Border Protection (CBP) has issued a ruling relating to the proper marking of the country of origin and states that paper labels are unacceptable on imported mugs that are going to be further processed. Click on the link below for the complete text of the ruling. Link

There are many variables that must be addressed to make a good finished product when ceramic enamel decals are fired on ceramic ware. The first item to consider is the ceramic piece itself. Manufacturers design ceramic items so they have the physical properties needed for the expected end use.

Aesthetics can affect the general look of a piece, but the clays used, amount of vitrification needed, and the glaze composition, all play a critical part in a good finished product. During firing, both in the initial making of the piece, and later after decorating, the body of the ceramic piece will expand slightly as it heats, and will contract a like amount as it cools. This expansion, referred to as the Coefficient of Expansion (COE), is very small, but critical in understanding crazing issues. The glaze used must be made with a COE very close to that of the clay body, so it will expand and contract similarly in order to "fit" the body. Glazed ceramic ware can be partially vitrified stoneware, fully vitrified ware, porcelain, or bone china. Each of these use different clay compositions, firing temperatures, and subsequently require different glazes. Because the glaze must match the clay body's COE, the glaze is formulated for a specific clay end cannot be substantially changed. As a result of this, ceramic enamel manufacturers have developed different enamels designed with specific coefficients of expansion to match the different glazes. Each of these enamels are designed with specific recommended firing temperatures and soak times, and are formulated to be compatible with only one glaze's COE characteristics, ie. onglaze colors for stoneware.

Decals are also made with different enamels, some for glass, some for onglaze with stoneware, inglaze for porcelain, etc. Each of these enamels are formulated with a certain application in mind, with a COE designed to match specific a substrate (in this cases, ceramic glaze). Problems arise when decals are made with enamels having a COE significantly different from that of the glazed ceramic piece. If this is the case, during the firing process, as the decorated piece starts to cool from its peak temperature, the enamel will solidify on the surface of the glaze, and the glaze and enamel will both shrink during cooling, but at slightly different rates. This causes stresses to build between the enamel and the glaze. If these stresses are great enough, the result will be crazing (cracking) of the decal. This can be easily identified as fine cracks that show up in the decal, but nowhere else on the glaze. To be clear, THIS IS A PROBLEM WITH THE DECAL, NOT THE GLAZE! As stated earlier, the composition of the glaze cannot be changed without adversely affecting the fit between the glaze and body. Therefore the only way to eliminate the crazing problem with decals on ceramic is to make the decals using enamels that have a COE that matches the glaze on the ceramic piece. Many people have tried using decals with a COE that is different than the glaze. In some cases, if the COE's are not too far apart, the decals may initially appear to be OK, only to craze sometime in the not too distant future. The stress will still be there, and these stresses will eventually be released in the form of crazing, due to further thermal cycles, such as going through a dishwasher. Others have found that pre-firing the ceramic prior to applying the decals, and then firing the decorated piece, will sometimes seem to work. Again, if there is a mismatch between the decal and glaze, the decal will eventually craze. The bottom line is, decals must be made with enamels that match the glaze! If in doubt, have the decal maker or enamel manufacturer recommend enamels that are compatible with the glazed pieces being used, and then verify the results through testing.

A small void of glaze on a fired mug is typically known as a “pinhole”. Pinholes in ceramics are the result of volatile organic materials outgassing during the firing. There are always some small percentage of organic materials in the clay of the mug bodies. During the firing, these organic materials will oxidize and the resulting formation of CO and CO2 will be driven out of the body, through the glaze, and into the atmosphere. Occasionally, the outgassing will cause a bubble to form in the glaze. When this bubble expands enough, it will break and cause a small crater in the glaze. While the glaze is still in a viscous liquid state, it will usually flow back into the ‘crater’ and fill it, thereby smoothing out the glazed surface. Sometimes, the bubble will break just as the cooling process is starting and if the glaze starts to thicken during the cooling, it can become too viscous and stop flowing before the crater has been filled and healed over resulting in a small pinhole.

One way the occurrence of pinholes can be reduced is to fire the unglazed mugs to allow the mug to outgas completely, then applying the glaze to the mugs and re-firing them. This added firing increases costs considerably. Because of the added cost and time, this process is usually reserved for high-end dinnerware. Almost all of the ceramic mugs used in the decorating industry are single fire and the pinhole issue is controlled as much as possible through careful firing. This allows the best compromise between acceptable quality and price. While all reasonable efforts are made to control the formation of pinholes in ceramic mugs, it is virtually impossible to eliminate them completely. This is generally well known in the decorating industry and accepted as the norm.