How Tough is a Cold Cast?

Making a decorative metal piece does not have to be pricey and cumbersome. Cold casting makes it easy, but artists should keep in mind that the reproduction will definitely be more brittle than metal.

Cold casting is a popular method of making faux metal casts. It involves mixing metal powder with a resin to create castings that give the appearance of solid metal. Rather than the hot casting method using molten metal in a foundry that is both expensive and time-consuming, cold casting turns out to be a quick and affordable option for recreating the look of metal casts. There is no risk of burns and other dangers either.

Recreating a figurine, prototype, hardware pieces, small run production pieces and other parts with cold casting is relatively easy. The requisite bronze, brass, copper, steel or aluminum powder is usually brushed, dusted or sprayed on the inside of the mold to form a thin and even coating. Then the resin is mixed and poured into the mold. (For smaller pieces, the powder can even be mixed in the resin itself.)

Once the resin is cured, it is demolded and burnished or abraded with steel wool to remove the binder and reveal the beauty of the metal filler on the surface of the cast. Keep in mind that when the metal powder is mixed with resin, it may take a bit longer to cure.

The same technique can be used to recreate the look of ceramic, wood or even stones like granite, marble and limestone. Tin powder can work well for achieving a pewter, iron or nickel silver finish.

Points to ponder

While a cold cast sculpture will replicate the exact look of the original metal, stone or wood piece, it will obviously not weigh the same. It is much lighter and some artists retain the light feature as it makes the ‘sculpture’ easier to handle. Otherwise the mold can be backfilled with fiberglass, iron or steel shots, sand or calcium carbonate to achieve the desired weight. Alternatively, the cold cast can be lightened by adding hollow glass beads.

Coming to the durability of the cold cast reproduction, it will definitely be hard and durable. The actual toughness will depend on the casting resin used to make the piece. All resins cure hard and epoxy resin is considered exceptionally sturdy. However, the strength and durability of a molten-crafted metal construction cannot be replicated. Therefore, care is required not to bang or drop the cold cast figurine.

The best choice

EnvironMolds offers a variety of fine grade cold casting powders that are 325 mesh grade - the correct fineness for cold casting - and can recreate a beautiful finish. Even the resin options are of top quality and will turn out strong and sturdy castings that can last long as long as they are handled properly.

In sum, cold casting with casting powders is the way to go to get the desired effect without spending a bomb or even bearing the risks of a foundry casting.

Clay Goes from Modeling to Ballistic Testing

Clay is as versatile as a material can get. Get to know the different uses of various types of clay that ranges from clay models, molds and casts to even ballistic testing of vests and varied weapons.

Clay enjoys wide patronage in the world of mold making. Clay modeling is very popular and is used for a variety of purposes. Apart from molds, this extremely malleable substance is also used for sculpting, mask making, special effects, animatronics and claymation. The best part about using Plastilina clay is that it is oil-based and non-drying. This makes the material reusable as well.

Apart from this, clay proves to be handy for various other unexpected uses too. For instance, small dabs of clay are used to affix the model to the base before making the mold. The same clay can be also used to fill the gaps around the edges of the model; this will give a good, clean edge to the mold. Even any spaces or holes in the model can be plugged with clay before applying the mold making material. It also serves well for sealing the edges of the mold box, so that the mold material will not seep out before it cures on the model.

Other types of clay

There is a special type of clay called ballistic clay. The distinct feature of this clay is that it manages to almost replicate the density and viscosity of human tissue. The close match makes it useful for estimating and comparing the destructive effects that various firearms and ammunition can have on the real human body.

The gel like substance is regularly used as a backing material for terminal ballistic testing – like the testing of ballistic vests. It will provide unmatched terminal ballistics data for all types of rifles, handguns, machine guns, muzzle loaders, air rifles and pistols, bows and crossbows. In addition to this, ballistic gel heads and torsos can be used to simulate the effects of various bullet wounds with reliable and consistent results every time.

Where to get them?

EnvironMolds stocks a fine selection of plasticine, ceramic and ballistic clays of all types and price ranges. The renowned choice of professionals – Roma Plastilina clay comes in several degrees of hardness and is suitable for almost any application. Then there are budget options from Del Milano and even sulfur free formulations from Chavant. The latter can be used to cast silicone rubber without any fear of interfering with the setting of the rubber.

Coming to ballistic clay, the art supplier offers ballistic clay and gel blocks along with dummy heads and torsos. The clay is clear, odorless, reusable, 100% synthetic and contains no organic materials. It is non-toxic and can easily be molded into any shape as desired. More importantly, it is completely temperature stable (up to 240℉) too. Moreover, Clear Ballistics does the calibration on the gelatin to ensure that each batch meets the FBI protocols for ballistic testing.

Learning the Mold Making/Casting Lingo

What is the negative image of a model called that you will make before making a positive replica? What are the holes on the top or bottom of a mold called? Know the terms that go with molds and casts right away!

The world of mold making, casting and life casting comes with its own plethora of terms and phrases. Familiarity with them is essential.

  • Mold – It is a negative impression of the model, usually in the form of a hollow cavity.
  • Cast – This is a positive duplicate of the model which can be in any other material or color as desired.
  • Cold cast – This is a faux cast – it is made of resin but can duplicate the look of metal, stone or wood.
  • Life cast – The three-dimensional representation of a live person – it can be the face, hands, feet, torso or entire body.
  • Pot time – Also known as working time, this is the time on hand to work with a material – it includes the mixing and application time - before it will start to set. After this, the material will not work properly.
  • Cure time – This is the time that the material will take to get completely cured. It can range from just a few minutes to hours or even a few days.
  • Shelf life - The period of time a material can be stored and remains suitable for use.
  • Mix ratio - The proper proportion (either by weight or volume) of material and catalyst (oftentimes referred to as Parts A and B) to be combined.
  • Shore hardness – This is a measure of the hardness of a given material or how resistant it will be to permanent indentation.
  • Release agent – A material applied in a thin layer to the surface of the model or mold so as to allow the subsequent mold or cast to be demolded easily.
  • Sealer – Another material that is applied on porous models to seal the pores and prevent the mold making material from getting absorbed.
  • Demolding – The process of removing a model or casting from a mold.
  • Parting line – A marking line which denotes where the parts of the mold should meet.
  • Keys – These are created at the ends of multi-part molds to join the different parts together to form a complete mold.
  • Spues – These are the small holes which will help release the air trapped inside the mold.
  • Pour hole – This is created as an opening to allow the casting material to be poured into the mold.
  • Viscosity – This is the thickness or thinness of the material and will dictate how easily it will flow. Less viscous materials are thinner and flow easily.
  • Pressure pot – Resins are usually cast under pressure that will compress the trapped air to miniscule size.
  • Vacuum chamber – The rubber mix is usually churned using a vacuum pump with vacuum chamber. The vacuum chamber will suck out the air and not allow bubbles to appear on the rubber mold or cast.

Armed with this detailed knowledge, get going right away!