Frequently Asked Questions

Although different clays have different densities a good estimate is 90 pounds per cubic foot. AutoStyle™ Industrial clay and Y2Klay are light weight (approximately 30% lighter) 

Concerns with mixing different clays are color, reactions to rubber, hard/soft areas and cohesion. A user may hit firm areas and then soft areas when moving tools through the clay. Proceed with caution. 

Some Chavant clays can be hand-shaped at room temperature, while others are very firm, and need to be heated to become shapable. Softening a firm clay with heat can make the warm clay easier to manipulate by hand or work with tools. All Chavant Clays can be softened with the application of heat and each clay has a recommended Softening Temperature that can be located on the product’s Technical Bulletin and in the Softening Temperature Chart found here. 

Do not overheat clay to temperatures above the highest temperature value for each clay, as excessive temperatures can cause clay components to overheat, burn, or scorch. Using a probe thermometer and observing the clay as it heats will also help to keep warming clay within temperature ranges. Watch and monitor your clay temperatures closely, never leave them unattended. Heating equipment should not be set above the highest maximum temperature of the clay to prevent it from burning. 

Sulfur-Based clay will discolor clay warming equipment and can build up (crystalize) on the interior of clay warmers and industrial ovens over time. 

Heat resistant gloves, long sleeves, and eye protection should be worn while working with hot clay to help reduce the potential for burns and injury.

Generally, a cooled clay solidifies back to its original hardness and may be heated and cooled many times. However, the repeated heating of a batch of clay will eventually cause a clay to permanently harden. Kneading a clay after it’s been heated and cooled (or running firm clay through a clay roller) can sometimes help in returning a clay to the hardness and consistency of its original preheated state.

Heating Automotive and Industrial Chavant Clays irreversibly hardens the clay.

Keep Heating Equipment clean of clay build-up and dripped clay to help reduce fire risk.

Heating equipment must be used in an area with mechanical exhaust fan ventilation.

Accepted Heating Equipment: 

Temperature-Controlled Crock Pots

Scientific/Laboratory Oven

Hot Box With Conventional Temperature Monitor

Warming Oven Dedicated To Clay Only (Do Not Use Home Oven)

Not recommended:

· Do NOT apply direct flame to clay.

· Microwaves are not recommended due to uneven heating and potential burning of skin and clay product.

· Double Boiling on an open flame is not recommended as water can easily disrupt clay mix.

· Heat Lamps and Heat Guns are not temperature controlled and can burn and scorch clay.

Some Chavant clay products can also be heated to a consistency soft enough to be spread across a surface. Trowelable temperatures  (on each product’s Technical Bulletin and the Softening Temperature chart) are very hot and can cause burns so a metal trowel (or similar wood or metal spreader) is needed to apply the hot clay safely. When troweling, a clay can be spread easily across a vertical armature surface. Perform a small scale test with hot clay against a non-critical sample of armature substrates first to make sure they are compatible. 

It is also possible to brush a lower viscosity (thinner) initial clay coating on armature surfaces. A small scale test against armature surfaces to check for suitability is always recommended.

Brushing Clay in a Mold:

The Brushing Temperature (on each product’s Technical Bulletin and the Softening Temperature chart) is the best temperature for the clay to hold a vertical surface without slumping when applied at thicknesses less than ¼ inch. Unlike the thick troweled clay, the Brushing Temperature has a lower viscosity and captures detail from the mold without voids or surface bubbles. 

As these clay temperatures are very hot and cannot be handled, a brush is needed to apply the hot clay. 

First an initial thin detailed layer of clay is brushed onto the mold surface first and allowed to partially cool. This process is repeated several times and additional layers of clay are brushed on top of each other to build up the clay casting until the desired overall thickness is achieved. A brushed clay casting needs to be thick enough that it can be demolded without cracking or breaking.

Pouring Clay To Make Solid Castings:

NSP and Castilene are the only two clay product series in the Chavant line that can be melted to a point of becoming liquid for casting or pouring. 

Both the NSP and Castilene Series can be heated to a liquid state that is a low enough mixed viscosity to pour into a silicone mold and capture fine detail. These clays have Casting Temperatures included on their Technical Bulletins and on the Softening Chart provided. 

Heat resistant gloves, long sleeves, and eye protection should be worn while working with hot clay to help reduce the potential for burns and injury.

Tips for Pouring Liquid Clay Castings:

· For best results, preheat silicone molds to at least 150F/66C prior to casting hot liquid clay. 

· Use at least 1lb of clay per casting session to help make sure you have enough mass to prevent melted clay from cooling to quickly (which can result in visible flow lines and loss of surface detail in the casting).

· Hot liquid clay should be mixed thoroughly prior to being cast into molds, to ensure that the clay is evenly melted and to reincorporate any separation in liquid material.

· Silicone molds can be put back into the oven for 1.5-3 hours after pouring clay into them to help allow entrapped bubbles to rise off the mold surface.

· After casting, please allow clay and mold to cool back down to room temperature (72F/23C) before demolding as an early demold can result in loss of details.  

· Smaller pieces of clay heat significantly faster than larger thick clay blocks. When casting clay, pouring your excess liquid clay into an extra mold (such as a silicone ice cube mold) can make it easier to reheat again quickly for your next casting session.

Pouring Clay To Make Rotational Castings Or Slush Cast Liquid Clay:

Generally, A Rotational Casting machine is used to continuously rotate a silicone mold until a hollow clay casting is created with a consistently even thickness and smooth interior. Several layered applications of liquid clay poured inside the mold may be needed to bring clay casting up to the desired total thickness. The clay casting is left inside the mold to cool and return to room temperature (73F/23C) before demolding. A silicone mold can be preheated to 150F/66C and secured on a Rotational Casting Machine while wearing heat resistant gloves, to help improve the surface quality of the clay casting when Rotationally Casting. 

To Slush Cast hot liquid clay, the clay is poured into a silicone mold and the mold is turned by hand continuously until the clay has completely covered the surface of the mold. Excess clay is poured out of the mold before cooling solid. This process is repeated in layers until the desired final casting thickness is reached to create a strong, hollow casting that can remain intact during the demolding process. A consistent thickness across the casting is needed as a thin clay part can easily deform, crack, or break under pressure.

Allowing hot liquid clay time to dwell (temporarily rest without moving) in the mold results in thicker clay layers as the clay firms and cools against the mold surface. Dwelling hot clay is an advanced and challenging Slush Casting process as unwanted excess clay will still need to be poured out before it cools to a solid state. It takes practice and deliberate turning motions (that will vary from mold to mold) to prevent unwanted clay from building up in the mold and cooling in place. 

Although all molds have unique configurations that have their own challenges, turning a smaller mold over and over by hand tends to be easier compared to a larger mold as you are ultimately handling less weight. Practicing the process of Slush Casting hot clay in a smaller silicone test mold first can help you build experience and observe how the clay cools in your studio environment or workspace before scaling up to a larger mold configuration. Practice can also help you avoid freeze lines (visible seaming) and loss of detail in your final castings.

Heat resistant gloves, long sleeves, and eye protection should be worn while working with hot clay to help reduce the potential for burns and injury.

Tips for Rotationally or Slush-Casting Liquid Clay To Make Hollow Castings:

· Prepare a metal scoop or ladle in advance to dispense liquid clay so that you aren’t trying to hold a mold and pour large amounts of clay simultaneously, which could result in spills and skin burns.

· Make sure mold rubber and rigid support shell (also called a Mother Mold) can withstand the temperature of the hot liquid clay.

· Hot liquid clay should be stirred thoroughly prior to being cast into molds, to ensure that the clay is evenly melted and to reincorporate any separation in liquid material.

· Once taken out of warmer, clay will quickly begin to lose temperature. Setting up your mold and work area closer to the clay warmer means more working time to pour and rotate your mold while your clay is in a liquid state.

· Rotate and fully coat mold surface while clay is still liquid by moving quickly and deliberately. Practice motion with empty mold before adding hot clay. If clay cools before mold surface is covered this can result in freeze lines (visible seems) where detail is lost from the mold surface or lines appear between the application of clay layers.

· Keep mold moving continuously and dump out excess liquid clay before cooling. Note: The surface of the mold and the low mass (thin) areas will cool fastest when rotationally casting. 

· Cooling clay has a change of appearance compared to wet liquid clay. Even though it may no longer appear liquid, the clay is still warm and can deform. Wait until mold and casting return to room temperature (72F/23C) before demolding.

· When Rotational Casting with a Rotationally Casting Machine, secure a cover over the mold’s pour area before rotating so excess clay does not drip out. Covering the mold is not Required when Slush Casting and hand rotating the mold responsibly.

Try water, Avon Skin-So-Soft (Original Bath Oil), WD-40, Goof-Off, turpentine, lighter fluid, multipurpose oil/wax solvents, Citrus/ D-limonene based cleaning fluids 

Sulfur is an inexpensive, non-toxic, soft mineral filler that enhances the surface texture of the clay.  Sulfur-free formulas are generally easier to make silicone rubber molds from.

Heating some Chavant clays in clay warming devices, often required to soften the material, can produce a distinct non-harmful odor. Many clients have successfully reduced odor emissions from clay ovens by attaching activated charcoal filters to an exhaust vent often found on ovens.

Activated Charcoal (aka Activated Carbon) Filters are available from various manufacturers. Check the Thomas Register under Filters: Activated Carbon. One model that we have seen is produced by Airfiltronix Corporation of Clifton, NJ. They can be reached at 1-800-452-8510 or through their web site www.airfiltronix.com.

In general, oil-based clay will oxidize and get firmer over time although it can remain workable for many years. Once opened, place clay in airtight container or wrap completely in plastic wrap and store away from sunlight or sources of UV to reduce oxidization and maximize usability. 

Some Chavant Clays are sulfur based which helps prevent the clay from experiencing surface oxidization and hardening. 

However, most notably the sulfur-free NSP series does not have an oxidization inhibitor. When the clay is repeatedly heated and cooled, oxidation is accelerated. The NSP clay series can become dramatically firmer over time and ultimately harden to a brick/stone like state that loses the ability to be shaped by hand. There is no way to reconstitute or soften the material after this occurs.

Modeling clay is normally used without skin protection, but it will be up to you to determine suitability. Please read the Safety Data Sheet (SDS) documents for our products before use. If you have a known allergy or sensitivity to sulfur, do not use sulfur-based clays. If irritation appears when handling sulfur-based clays, it is most likely an allergic reaction and use should be immediately discontinued. Often these symptoms will first appear as mild skin rashes. Most often, practicing good hygiene, primarily washing hands and clothing will eliminate this symptom. 

Wash hands with soap and water after using clays.

Some of these clays, contain sulfur, which may cause a burning sensation in the eyes of some users. Although not dangerous, it may be uncomfortable 

Red Clays (clays containing Iron Oxide) can also stain hands and clothing. 

Typically, Chavant clay products are used mid-design process or early in the creation process (also called ideation) to meet a specific shaping need. What is a Modeler looking for in a clay? This is difficult to answer because every artist is different, and some artists are looking for a specific outcome while others may be developing their process through experience and exploration. Establish which type of application you have and where you are in your developmental process. 

Creating a checklist can be helpful for deciding your next steps and identify overall needs relevant for your unique model. Documenting your questions and answers can also help you keep track of your progress as well as look ahead to next steps and to build a material and tool list before you start. For example, is this sculpture the ultimate result of your project or is it a study to help you progress your overall project? How will this finished piece be used for example exhibited, molded, digitally scanned, post-finished (painted/sanded/tooled), or transported? Is there a specific clay feel you are trying to match too, softer or firmer? Are important/specific tools being used that need to work the clay? Will the clay need to be adhesive and stick to an armature surface? What is your armature and base made from (example: aluminum wire and melamine board)? Are there potential challenges you can identify that you will need to overcome with this unique project? Are you going to need to store your clay model over time?