Chapter 4: Sculpture & Casting Media:
An overview of contemporary choices.

Medium Transfer is the term for various methods of changing the material a LifeCast™ is made of into another material, from plaster to wax for example.

Earthium™ excels at this type of application since it is fast, accurate and intended to be temporary. One such use would be to make a LifeMask™ and cast it with more Earthium™ instead of anything permanent. This will give you a quick, positive LifeCast™ which can be covered with ArtCast™ or some type of plaster, resulting in a mold which can be used for ceramics, plastic or wax, a temporary but highly detailed medium.

Then cover that with latex for a permanent mold which will produce dozens of copies from a variety of media. A wax original can also be used for making a fine art metal cast without the major cost of extensive foundry work.

The following general information on casting media will provide you with an array of choices. There is no attempt here to be comprehensive on any of these mediums, merely descriptive. We can supply most of these materials or refer you to sources for items you need. Please contact us for pricing on any special order items, services or referrals that you may need.

Plasters:

These are some of the easiest and safest permanent sculpture mediums there are. Plaster is prepared by heating or 'calcining' gypsum (calcium sulfate).

The basic difference in strengths depends on how this is done and what it is then mixed with, usually some form of lime (calcium oxide) which combines with water to form calcium hydroxide (hydro means to get wet). The smaller and more regular the crystal shape, the tighter and stronger they pack in the final casting.*

Other additives such as lime, Portland cement, water based glues, acrylic and bone emulsions, fibers, coloring, and so on have generated dozens of different product names with unique performance characteristics. Our ArtCast™ statuary cement is one of the most versatile in this group.

Many areas of lifecast.net describe its basic uses for pouring final sculptures, slush castings and shell or "mother molds" (see Chapter 3). In addition;

Plasters:

• Burlap or hemp fiber may be run through a mixture or "slurry" of ArtCast™ and water. These are then shaped or applied over a rough structure which approximates your design (also called an armature). This reduces the amount of material needed and reduces the weight of your work while increasing its strength.
• ArtCast™ may be mixed in batches, each with a little water based or dry pigment to give them separate colors. When alternately poured or spread the effect is one of natural stone with striations of color. (see Tips, Tricks and Finish)
• The setting time may be speeded up by a small addition of common table salt (sodium chloride). This is very useful in LifeCasting™ for shells where you want to get your model out as quickly as possible. You should not use salt in final castings since it causes a reaction called efflorescence which will eventually damage the surface of the sculpture.
• Setting time can also be hastened by the addition of terra alba (literally, "white earth") which is a common name for calcium sulfate or gypsum, an inexpensive and harmless chemical. This will however weaken the cast slightly.

Concrete:

Concrete is used extensively for architecture and occasionally for the casting of large scale sculpture. It is an aggregate of sand and gravel with various sticky materials (lime, Portland cement, tar, etc.). Some harden upon drying, others by becoming wet.

Concrete is characterized by long mixing times and, in some cases will remain fluid until you stop mixing them, at which point they begin to set.

Concrete:

They also have extended setting times, frequently several hours to several days.

Concrete also does not capture any fine degree of detail, such as fingerprints. It is not particularly useful for lifecasting with out materials.

Wax:

Waxes come in an enormous array of formulas, each with its own unique applications. Nearly all 3 dimensional items, from toys to turbine blades to bronze sculptures either begin as wax or go through a wax phase in their creation. It is by far the best medium for capturing the finest detail of a LifeCast™.

It is usually not a final medium except in candle making or temporary displays which will not be handled. A wax model must be transferred into another, permanent material.

Waxes are usually solid at normal temperatures but liquefy upon heating. This causes some problems with typical mold rubbers and plastics. Pouring a hot wax into a cool mold frequently causes the wax to solidify too quickly, causing "freeze plugs" in narrow areas and preventing the wax from duplicating the entire mold.

The advantage of using wax in an ArtForm™ or Earthium™ (f/x) mold is that our molds are mostly water! They can be heated in a microwave oven very quickly to be as hot or hotter than the melting point of many waxes. When the wax is poured, it does not solidify until the entire mold does. This creates LifeCasts™ of absolutely stunning detail, capturing every skin pore, every crease, every fingerprint.

These can then be transferred to metal, such as bronze at very reasonable cost, since they are already in wax. If this interests you please refer to our Services section. You will not encounter much choice of this medium in typical art supply stores and must search out specialists in this medium, such as those who supply universities, foundries or industrial manufacturers.

Wax:

The best waxes for lifecasting are those which become very liquid at temperatures less than the boiling point of water. They tend to be quite brittle in their solid states. They are not malleable.

Of the common art & craft waxes which you may find in the better art supply stores;

• Paraffin is a petroleum product which is not water soluble. It is liquid at a high temperatures with a boiling point above 300 degrees C which pours easily. It is used primarily for candles and can create some very interesting LifeCast™ candles. It is stiff, brittle an retains moderate detail.

• Beeswax is a yellowish substance secreted by bees to create their honeycomb. It is solid a room temperature but melts quite easily and as such cannot be handled much. It is also used for candles but is excellent for polishing lifecasts made in cements such as ArtCast™.

• Microcrystalline is a dark brown, modeling wax made of petroleum distillates and other additives. It is an excellent medium for modeling shapes and is used similar to modeling clays but, never dries out. It use for casting is limited because it is not designed to become liquid. Upon heating it becomes very loose and pliable, even in your hands but, cannot be poured into a mold.

Also, microcrystalline never becomes very stiff unless frozen and must be used over an armature for any sizable work. A good way to get the characteristics of two or more waxes is to melt them together, microcrystalline and paraffin for example will give a pour able wax which is less brittle.

"Cold" Cast Metals & Artificial Stones"Cold" Cast Metals & Artificial Stones are misleading terms. They are primarily plastic resins which are filled with either metal or mineral powders which simulate the real things.

While they can be very beautiful and useful to lifecast sculptors, they behave like and have the limitations of the plastic resin which is used as a binder. These are described below.

Polymer and Monomer Resins (Plastics):

Plastics are one of the most (if not the most) important developments of the 20th century. When you understand how many other things depend on these complex molecules it staggers the imagination.

The term itself, is plastic or able to fit many uses. In one sense all of the visual or sculptural arts can be called "plastic".

(Plastics):

For the LifeCast™ artist the word is an oversimplification. Many mediums, very different from one another are all lumped together into the category of "plastics".

A more accurate term is resin which is also a simplification but, adequate to our purposes.

There are two basic types described below.

1. Thermoplastic resins become soft and/or fluid when heated and return to a more rigid state upon cooling, similar to wax. These typically cannot be used in molding except for slush casting, or its cousin press/ram casting.

As such they are not as useful to us as the second type. Three common types are;
• Hot melt glues which are actually various types of plastic
• The trade named modeling medium "Friendly Plastic©"
• Various brands of polymer clay such as "Sculpty®"

2. Thermoset resins are those which harden upon being heated by a chemical reaction.

These "plastics" consist of two parts, a resin and a catalyst which are mixed together as liquids and react to form a solid over time. Additives can be used to alter their characteristics. These are very useful in lifecasting.

The most readily available are described below.

Polymer "Clays":

Polymer "clays" with remarkable abilities have appeared in recent years. They can be modeled by hand or with tools then baked at low temperature for 10 to 30 minutes to become hardened. They usually have brilliant colors which are permanent.

Polymer Clays:

They are useful for press type slush casts and also for layering on top of a LifeCast™ made of another medium. These thin layers can be heated with a hair dryer to the temperature needed without baking. When cool they will harden to a durable, colorful surface.

Polyurethane:

This is a very liquid, light, strong plastic which retains excellent detail and can be highly weather resistant. It consists of the urethane resin and an isocyanate catalyst which become very hot upon mixing, thereby forming the solid. Like all thermoset plastics, once the reaction occurs it cannot be reversed.

Most polyurethanes are used as foam for insulation, padding, etc. This of course is not good for detail retention and is caused by a reaction between water and the isocyanate catalyst.

Polyurethane:

When they mix, carbon dioxide bubbles appear, creating the foam. For our purposes, this is bad and difficult to avoid since we pour into molds that are mostly water.

Many of these foaming problems can be avoided by the proper use of the specific brand. Another alternative which will work with all polyurethanes poured into our molds is to add our WaterTrap™ moisture scavenger to the liquid before pouring.

See Products section for more WaterTrap™information.

Polyester:

Polyester is a transparent or translucent resin which is also mixed with a catalyst to create a solid. Frequently this type of plastic is used for "floating" coins, sea shells, etc. in solid geometric shapes as coffee table artifacts or tourist collectables.

This is also the type of plastic that is used to simulate marble (by filling the resin with calcium carbonate) and the so called "cold" cast bronzes that have become popular (by filling the resin with bronze or copper powder).

It can make some very interesting lifecasts which refract light through their shapes and simulate more exotic mediums.

Polyester:

It is also somewhat hostile to water and must be used a certain way in our molds;

• Use Earthium™(f/x) at a medium to low Part B ratio (see Earthium™ instructions) which will make it set slower but also prevent moisture from escaping as quickly.
• Use slightly more catalyst than recommended to set the polyester resin faster (too much will crack the casting - see manufacturer's guidelines).
• Get the casting out of the mold as soon as it can hold its own shape. The surface may still be tacky since the moisture may prevent it from setting.
• Let it air cure for a day and if still sticky, spray it with a clear sealant.

Silicone*:

Silicone can be fluid, resinous, rubbery, solid, water repellent and very stable at high temperatures. It is widely used for molds and casts where durability is crucial.

As expected silicone mediums are expensive but, worth every penny when the need arises.

Silicone:

PolyArt™ silicone is specifically formulated for use with ArtForm™ and Earthium™ (f/x) and creates castings or molds with a soft, flesh-like feel and extreme detail. It sets fast and can be tinted to resemble any shade of the human color spectrum. It is also completely safe when cured for nearly any use imaginable.

Epoxy:

Epoxies of various components are extremely strong, though expensive. Many of them work very well with our mold mediums.

Epoxy:

The epoxy putty versions can be used for repair of cast bubbles, in slush casting and many other sculpture applications.

Preparation & Use of Thermoset Resins:

The mixing of thermoset resins (components which harden by chemical reaction) can be a challanging process without the right equipment. Not only are the ratio measurements very critical but they must be completely blended for predictable results.

Some are so sensitive that even mixing them in an absorbent container or with a porous stirring tool, like a wooden paint stick will ruin a batch.

Air bubbles (see Basics 3) are also especially difficult to control without using a vacuum chamber. Once again our versatile BlendBag™ has proven itself uniquely useful with most plastics.

Preparation & Use of Thermoset Resins:

The following procedure minimizes or eliminates many of the typical problems associated with using thermoset plastics.

A note about the BlendBag™ cap:
• Although we provide caps for this technique in the WebStore you can cut the end off any plastic bottle that suits your application and use that.
• It is best to find one with a pull up, "Sports Nozzle" end to have greater control over flow. Be sure to use one with a large enough opening for the viscousity of the material you will be using.

Other types of caps would alter this process slightly but you should have the idea.

Although we are using PolyArt™ specifically for this example description, the process and issues are nearly identical for all thermoset resins.

The distinctions will be in the ratios of the parts (usually 2) and the amount of Working time allowed for the specific plastic formula.

1. Pour the amount of silicone base (Part A) into the bag as required for your project.

2. Add PolyArt™ color (if needed). Our tints are concentrated so use small amounts.
• Blend per Step 3 then add more until the intensity you want is achieved.

3. Purge the air & pinch the bag 4-5 inches from the end.You want to keep the top few inches clean on the inside for the next step.
• Blend color thoroughly.

4. Thread the top 3-4 inches of the bag through the bottom part of the cap. Arrange evenly around the inside & fold over. Attach the cap to ensure it fits then remove it.
• If needed hold the bag with a rubber band.

5. Add catalyst. Usually this is a 10:1 ratio by weight (10 A:1 B).
• Color shown is for illustration only. The PolyArt™ catalyst is clear.

6. Do the next 2 steps quickly.

Quickly re-attach the cap. Since this was already done in step 4 it should go on easily this time.

7. With the cap open "burp" all the air from the bag. The idea is to create as much of a vacuum chamber as possible.
• Don't let the pool of catalyst sit in one spot for too long.

8. Close the cap. Again blend the fluids thoroughly. Be sure to get into all the corners.

9. Hang or sit the bag upside down for 4-5 minutes. Remaining bubbles will float up, away from the nozzle.
• Open and pour.

Latex (Rubber):

Rubber began as the sap or milky juice (latex) of certain trees and plants. That is still the basis for most rubber products such as rubber cement, rubber bands, erasers, electrical insulation, gloves, tires and, of course, condoms. There are now several synthetic rubbers as well but, for our purposes, latex is the only type of rubber useful to LifeCasting™.

Latex is gathered from trees similar to the way maple syrup is, with taps and buckets to collect the liquid. It is very watery in its native state and must be distilled onto a thicker fluid. Latex tends to coagulate in contact with air as it thickens so some form of solvent, like ammonia is added to prevent it.

The purest form of latex is used by dipping a shaped armature, like a ball for balloons or a hand shape for rubber gloves into the liquid. It then solidifies on contact with air and evaporation of the solvent. This dipping process is repeated until the desired thickness is achieved but requires exposure to air between each layer.
• For this reason you cannot just pour rubber into an ArtForm™ or Earthium™ mold, there is too much moisture on the contact side to allow the latex to oxidize. Latex can however be used on a finished LifeCast™ in cement, plastic, wax, etc. to make an inexpensive mold for repeated castings or prototypes.

Mold making latex is combined with fillers and chemical modifiers to give thickness or "body" to the medium. This combination allows a mold to be built up to the needed thickness quickly and economically by painting on layers.

Latex (Rubber):

Frequently ground up rubber powder from old tires is added in some areas to fill in undercuts inexpensively.

Another discovery about latex was made by Mr. Goodyear while in debtors prison (he never benefited from this priceless discovery). If latex is heated in combination with sulfur it becomes extrodinarily elastic and durable. This is called vulcanization and can make latex either very flexible or very stiff.

Known as "casting latex" the rigid form of it was used extensively to make doll parts and other small items before much was known about polymers (a technical name for "plastics"). It discolors in time which is why antique dolls today have a typically yellowish tint.

Casting latex is used similarly to ceramic or clay "slip". It requires a mold that can withstand heat and absorb the excess moisture. These molds are made of gypsum cements, like our ArtCast™ which, if prepared correctly can "wick" the moisture away from the mold surface and pass it to the outside where it evaporates.

The flexible version of casting latex is still widely used today. Highly skilled special effects (f/x) artists use it to make prosthetic devices for the actors to wear as part of their make-up and costumes. The next time you see a "Klingon" or some type of biological machine, chances are they are wearing clever prosthetics made possible by Mr. Goodyear's discovery.

Ceramics (Mineral Clays):

Ceramics is the general term for the art of making things from clay, earthenware or porcelain which typically includes treatment by heating to relatively high temperatures. This can be done by modeling or by casting, our area of interest.

Clay can be pressed into molds, rammed between die molds (see Chapter 3) or poured as a liquid which is called "slip". Slip casting must be done in a mold which can absorb the moisture from the clay slip and pass it to the outside surface where the moisture evaporates. This "wicking" process leaves a deposit of clay (called the "body") around the inside of the mold. The longer the slip stays inside the mold the thicker this body gets.

When these walls of clay get to the desired width, the still liquid slip in the center is poured out to be used again. The residual body is unveiled, touched up and usually, depending on the type of clay, any additives and the artist's methods, baked or "fired".

This initial heat treatment is called "bisque". Later, the bisque artifact is coated with glazes and fired again, sometimes several times to create finished piece of great beauty. And, in recent years the almost, science fiction abilities of modern ceramic technology has become legendary.

Ceramics (Mineral Clays):

In lifecasting the process can produce stunning works of art but, it all has to go through the only kind of mold that has the needed characteristics – plaster. One way or another you must create a plaster mold of your LifeCast™ sculpture to hold the clay slip.

Fortunately this is easy to do with the Earthium™ since it can perform as both temporary mold and cast with no compatibility problems with any type of plaster. Of course the typical approach of pouring either our ArtCast™ or other type of gypsum plaster into an Earthium™ mold will generate a positive which can then be sculpted and remolded in plaster for ceramics.

That positive must be coated with something to prevent sticking which can obscure fine details. This approach also limits the complexity of shape since the neither the mold nor the object is flexible.

More interesting, is to use the Earthium™ as the casting medium, capturing even the finest detail. This generates a slippery, temporary positive which can be directly coated with plaster with no sticking or loss of detail. Plus this method is much faster.

Chocolate:

Chocolate is one of the most fun mediums to use in lifecasting. The key to success with casting edible sculptures is to begin with good quality chocolate, one with a high proportion of cocoa butter. These never get extremely liquid more like a thick pancake batter, so don't make your design too complex.

Pay extra attention to avoid the possibility of air traps.
• Make the LifeCast™ mold with a low water to powder to water ratio, no more than 2 : 1 with the ArtForm™ (less if possible). Earthium™ (f/x) ratios can go up to a 3 : 1 (H2O : A) ratio as long as the Part B is kept fairly low.
• After the release of the object from the mold, put the mold in the freezer as you prepare the chocolate. You don't want it to freeze, just get very cold for about 10 minutes.
• Melt the chocolate by cutting it into small pieces and heating it gradually in a double boiler. Do not use direct heat in a pan, it must be done gently or the ingredients begin to separate. A microwave may be used as long as you stir the chocolate frequently as it heats.

Chocolate:

• When as liquid as possible get the mold from the freezer and pour in the chocolate. It will be too thick to tap out the bubbles but surface ones can be minimized by turning the mold and letting the chocolate coat the inside evenly, then fill the remainder.
• Put the chocolate filled mold back in the freezer to harden. The chocolate will harden from the outside in. If you want a hollow cast, to fill with jelly for example, wait long enough for the thickness you want and pour out the center, then return it to the freezer. In a few minutes fill it with jelly then seal off the top with more chocolate. (Fingers made this way are fun, gruesome Halloween treats if filled with a red jelly to simulate blood when they are bitten into).

Dark or brown chocolates will sometimes have white areas where the coloring has separated from the surface. This can be touched up if necessary with food coloring or confectioners glazes.

White chocolate will have no such discolorations and will generally make better LifeCasts™. For a marbled effect you can mix white and dark chocolate.Chocolate will melt in your hands and this can be prevented by painting on a coat of confectioners glaze. Bon appetite!

Ice Sculpture:

Ice Sculptures are made by mixing a small amount of alcohol into the mold. Any type of alcohol with no sugar or other flavorings will work, isopropyl, even vodka!

The goal is to raise the freezing temperature of the mold, which alcohol does. The mold is filled with water and put in the freezer.

Ice Sculpture:

The water of course will freeze solid but, the mold will not be quite as hard, making it removable.

Relief and two part molds of course, don't have to be destroyed to unveil the ice casting, making clever drink coolers.

Go To Chapter 5: Advanced Techniques:
Precision Lifecasting & Other Approaches

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