Varied Uses of Plaster

 Plaster is a simple powder that is mixed with water before use. The material cures slowly to capture the shape in a solid form. This plaster can be used in varied ways to suit different purposes in the arts.

Plaster is a humble white powder made with a combination of lime or gypsum with sand and water. It is mixed with water to form a stiff paste before application. It dries to a solid form in some time. It is usually known as plaster of Paris as the gypsum was mined in abundant quantities in Paris.

The most common use of plaster mix is to coat walls and partitions to make the surface smooth. It is used to make false ceilings apart from stucco work and rendering. It also lends itself well for decorative architectural moldings like cornices and corbels.

Plaster is also used in the medical field to make casts for immobilizing broken bones and supporting the fracture till the bones can set properly once again.

A variation of the regular plaster also finds its way into the world of mold making and casting. This is different from the regular plaster of Paris which tends to become chalky and flaky over time, does not hold detail well and is hydroscopic in nature.

The art variant of plaster is harder which allows it to capture crisp details and set to a smooth solid. Yet it can be carved or tooled as desired. This is used in mold making and latex slush molds while plaster bandages are used to make shell molds or even form molds.

Plaster can be used for general mold making, but care should be taken as the material tends to emit heat due to the chemical reaction. Therefore, it can damage the product or harm the model when applied directly on the body. Some people have been known to get burns when plaster is used in large volumes!

A better application of plaster is for making the life castings. The plaster mix is poured into the alginate or silicone body mold and allowed to cure. After demolding, it turns out a bright white life cast that is a spitting replica of the original body part. It can then be finished as required before being put up for display.

Plaster is coated over gauze to form plaster bandages that can be used to make shell or mother molds. The wet bandages are smoothed out over alginate or rubber molds. They dry to a rigid form and thus lend the required stiffness to the flexible molds that would otherwise flop over themselves making it difficult to cast properly. The same bandages can also be used on the skin to make rough body part molds like the abdomen as they do not have much detail. Artists also use the same technique for making a face mold for making masks.

EnvironMolds offers a range of plaster options for pottery, casting and the ever-popular Plaster of Paris bandages.

Difference Between Plastic and Silicone Molds

Which is better – plastic or silicone molds for making castings of resins and other materials? Both options come with their own pros and cons. Generally, silicone ones are preferred by professionals.

The technique of making a cast begins with a mold. The casting artist will either make a mold or use a ready mold for making the cast. The casting material is usually poured into the mold and allowed to set before being demolded. Once it has cured properly, it is finished and is ready for use. How to make a mold for the casting is another story for another day.

However, here we shall take a look at the type of molds to be used for making a cast. Let’s consider plastic and silicone molds for instance.

Plastic molds usually have a lot going for them. They are easily available in the market in a variety of shapes and sizes. They are flexible, reusable and quite inexpensive at that. Being quite easy to work with, these molds are considered apt for novices stepping into the world of casting. Even if the molds get damaged, they can be easily replaced or even discarded if someone loses interest in the hobby.

On the other hand, silicone rubber molds are more sophisticated and top quality molds that are preferred by professional casting artists around the world. They may seem like a substantial investment initially, but this does pay off in more ways than one.

The biggest thing working in favor of silicone molds is that they can be customized as desired. The mold maker can make single or two part molds of any item that is to be replicated as a cast. However, making a plastic mold calls for specialized techniques and equipment for working on vacuum forming sheet plastic around a template. Therefore, making casts from plastic molds can be limiting based on the ready molds available.

Then again, casts made in plastic molds do not turn out glossy enough. The molds tend to get scratches easily, which also affects the quality of the castings. The surface that is touching the mold will have to be recoated with either the casting material or a sealer to make it shiny. On the other hand, castings from silicone molds have a smooth and shiny finish that is pleasing to the eye.

These molds also lend themselves well for making complex castings. Demolding is especially easy even for complicated shapes as silicone does not stick to anything except itself. It should be kept in mind that silicone molds are extremely durable, but only as long as they are cleaned and stored properly.

EnvironMolds offers a range of materials, supplies and equipment including a great selection of high quality silicone rubber formulas that are suitable for both mold making and casting. Indeed, most silicone mold rubbers can double up as casting rubbers too. However, artists should bear in mind that silicone rubber should never be cast in silicone molds as they will tend to stick to each other.