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Tin Silicone    SILICONE RUBBER 

There are two main types of silicones for mold making and casting applications:
TIN cure and PLATINUM cure.

Tin Cure Silicone
Tin cure or condensation cure silicones are basic two-part systems that yield accurate, chemical resistant molds for resin, foam, plaster, and wax casting applications. Of our silicones, Tin cure silicones are the easiest to work with and do not inhibit (fail to cure) easily. Tin Cure silicones such as the 70 series RTV rubbers require an accurate gram scale for mixing.

Most Tin cure silicones such as 70-25 or 70-30 may be thickened with Tin-Thix for brushing onto vertical surfaces.

Tin cure silicones make great production molds but they do have a shorter storage life or "library life" than platinum silicones. As Tin cure silicones age they lose elasticity and become brittle. Tin cure silicones such as 80-30 exhibit longer library life but archived molds for wax patterns (art bronze foundry work) may require a long lifespan of up to 20 years or more. We recommend urethanes (such as the 74 series) or Platinum silicones (Platsil® 71 or 73 series) for molds requiring an extended library life.

Tin cure systems, such as 80-30 or 70-30 are preferred for large sculptures or sculptures that might otherwise contaminate a platinum silicone. When in doubt, a small test cure is recommended to determine whether or not contaminates may be present on a pattern.

Platinum Silicone   PLATINUM SILICONE
Platinum silicones, or addition cure silicones, cure with virtually no shrinkage to a durable, long-lasting, chemical resistant rubber. Platinum silicones are popular with the prototyping industry due to their incredible accuracy and long library life.

Most Platinum silicones such as 71-20 may be thickened with Plat-Thix for brushing onto vertical surfaces. Low viscosity silicones, like 73-25 or 71-11, must be thickened with a more potent thickener such as TinThix.

Molds made with Platinum silicones achieve the highest level of detail. Platinum silicones are recommended for resin casting, foam casting, and archived molds for foundry patterns. Platinum silicones are easy to contaminate if proper care is not taken in surface preparation, mixing, or weighing. When in doubt, a small test cure is recommended to determine whether or not contaminates may be present on a pattern.

Platinum silicones yield excellent results but require a higher level of experience and patience than Tin cure or Urethane rubbers.

73-20 is a great starter silicone as it is low viscosity, fast curing, and 1:1 ratio making it ideal for small projects and model reproduction. Try our new 73-20 molding ans casting kit as a great way to get started molding and casting.

7430 Mold

7430 Mix




BITY Mold Supply offers several options for urethane mold making.

Polytek® rubbers such as the 74 series are popular for both poured molds and brush on molds. 74-30 is a very popular rubber for art bronze wax patterns and plaster casting.
74-45 and 74-20 are relatively new bright yellow rubber compounds that are immensely popular with cast-stone and veneer stone shops.

So many numbers... which one is which? What's the difference?
The last two digits in the series number denote the Shore Hardness of rubber materials in the 74, 75, and 77 series. 74-30, for example, is a 30-durometer-urethane rubber, 75-60 is a 60-durometer urethane rubber and so on. Polytek® urethanes are available in a range from a shore "A" 20 to a shore "A" 95.

The Poly 74 and 75 series offer easy mix ratios and excellent working properties. All rubber materials in this series are either 1:1 2:1 or 1:2.

The part "B" in this series will usually require stirring before use and is labeled as such on the containers. Without accelerators these rubbers will cure overnight at room temperature (RTV).

The Polygel series is formulated for brushing or spraying. Polygel is offered in a 35A durometer. Polygel rubber self-thickens when mixed to form a brush-able paste.

Making a brush-on mold?

74 and 75 series rubbers may be thickened to a brush-able paste by adding PolyFiber thickener or fumed silica. PolyGel series is self-thickening but may be thickened further with the addition of PolyFiber.

Important! When making brushed on molds, it is important to avoid delamination (layers peeling apart) by working fast and not waiting too long between coats of rubber. Urethane bonds best to urethane when it is fresh so it is imperative to move fast in order to insure a good chemical bond between layers of a brushed on mold.

How do I accelerate a urethane rubber?
Urethane mold rubbers are heat accelerated or they may be chemically accelerated with the addition of 74/75X. Adding part X will not affect the cured properties or mold life of urethane mold rubbers.

How long will my materials last once they are opened?
Urethanes are contaminated by moisture. Your shop environment is critical to the life of the product. The dry, arid climate of the southwestern states (such as west Texas or New Mexico) is best for preserving mold rubber. Humid climates such as Houston, or Dallas Texas will drastically reduce the life of your opened materials. Air conditioned shops are helpful but we recommend that you spray PolyPurge into the part A of all urethanes after opening. This will replace the moist air with a dry gas.

MoldGel Alginate


Hollywood Impresions Alginate


BITY Mold Supply offers the finest and most complete line of life-casting supplies for head casts, hand casting, and body molds.

Accu-Cast Alginates and PlatSil Gel-10 skin safe silicone will give you a variety of life-molding options.

Accu-cast Alginates are recognized as one of the best performing alginates for lifecasting projects.

Accu-Cast 380-CC is the alginate we most recommend for doing hand and feet castings. The 380 will turn bubble gum pink once mixed with water, but when it is almost set up it starts to turn white. It is great for keeping the attention of kids! Accu-Cast 380-CC has a 3 minute working time at 80ºF water temperature.

Accu-Cast 590 is great for doing face castings and hands for those who want a longer set time than the 380-CC allows. 590 has a 5 minute working time at 90ºF water temperature.

Accu-Cast 880 offers a 8 minute working time at 80ºF water temperature, which makes it great for headcasts, and body casting.

The Accu-Cast alginate family would not be complete without a dental grade alginate. Use Accu-Cast 270-D for making accurate molds of teeth and the interior of the mouth. 270-D is a fast setting dental alginate.

GENESIS "Prosthetic-Grade Cream" Alginates are used by many of the big special effects houses in Hollywood and elsewhere. "Prosthetic-Grade Cream" Alginates mix smooth and thick with very little drip. The Genesis V "snap sets" at about 5:30 to a very firm (almost hard) rubbery solid while still being very flexible. The Genesis X "snap sets" at about 10 minutes with 70ºF water.

Wax, Monster Clay, and plasters (such as Hydrocal, Hydrostone, and Ultracal 30) may be cast into all of the alginates that we carry, as well as PlatSil Gel-10 and Gel-00 silicones.

PlatSil Gel-10 is a Skin Safe Platinum silicone that has many purposes, including lifecasting. Gel-10 is great for super accurate lifecasts that can be used as permanent molds since they do not have the short lifespan inherent in alginate materials. When lifecasting with PlatSil Gel-10 you need to use TinThix or PlatThix to thicken the silicone and PolyFiber is also useful for the additional layers.



Plaster Bandages


As any experienced lifecaster will tell you, getting alginate to stick to itself is next to impossible. This unfortunate fact of life makes large casts difficult and requires careful planning and several skilled, fast helpers. Algi-bond bonding agent allows you to break the rules. Mix-up a batch of Algi-bond and apply it onto the alginate that has cured and apply fresh alginate. Algi-bond creates a strong bond between old and new layers of alginate.

BITY Mold Supply also offers extra fast setting Plaster Bandages in all widths, including 4", 6", 8", and 12", all in 5 yard lengths. Plaster Bandages make great lifecast support molds and may also be used for fast mother mold construction on rubber molds.

We also carry Bald Caps, and petroleum jelly, as well as Alginate Release which is a water based release, that is hypoallergenic, and made with all natural ingredients, that washes out the first time unlike petroleum based releases.


We carry Poly Latex 60, a high quality, brushable latex for making concrete molds, as well as False Fase Latex which is a liquid latex for meant for slosh casting. False Face latex is great for mask making. See our online catalog for pricing.

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