The Ins and Outs of Latex Rubber

Latex rubber is an artist’s weapon that can be wielded in varying manners. The properties and versatility of liquid latex rubber are to be experienced to be believed. Let’s find out more about this….

Liquid latex rubber is a versatile product that lends itself well to varied applications. The wonderful part about the rubber is that it is suitable for making both molds and casts. Changing the viscosity will change the application – latex molds require more thick and viscous formulations than casts. The degree of flexibility of the latex can be further controlled by adding an appropriate filler during the casting process.

Latex mold rubber is commonly used for mold making as it is economical, durable and easy to use. The molds will be tough, tear resistant and can be reused multiple times. They are used to cast plaster, polyester resin, urethane and even abrasive materials like concrete.

On the other hand, the casting variant of latex rubber is used for making hollow molded rubber articles like toys, balls, props and even display articles. It enjoys great patronage for making masks, puppet heads and even special effects like wrinkles, scars and gashes for theatrical work.

Latex rubber can be brushed, sprayed, poured or dipped for making the molds and casts. Brushing requires successive coats and sufficient time should be allowed for drying between each coat. This process is continued till the desired thickness is obtained. Spraying will also involve a similar process.

Latex is usually cast in plaster molds because of the porous nature of plaster. When the rubber is poured into the mold, the plaster sucks the water out and leaves a thin latex skin behind. Slip latex casting is a commonly preferred method as it is comparatively easy and does not leave any brush marks either.

When it comes to demolding the latex mold or cast, an easy trick is to dust the latex with talcum powder before peeling it off slowly. The powder will keep the fresh latex from sticking to itself. The latex mold will need to be supported before casting so that the flexible rubber can retain its shape.

Latex rubber is also used to form a protective coat on different items. The latex coat can make fabrics waterproof. It can also form a protective covering on tools that will provide a sound and comfortable grip even while insulating them against electrical hazards.

The most common use of latex rubber is for making a latex mask. This can be used for special effects in movies or even a fun element for Halloween and other occasions. It is usually cast in a face mold made of plaster bandages and then the desired characteristics are built on it step by step.

Other tips to keep in mind when working with latex rubber is that it contains a good amount of alcohol. Proper ventilation is required and do not inhale it too deeply or frequently. Similarly, the rubber will become unusable if frozen. Store it carefully in the winter months of the year.

The Fiber-Reinforced Version of Alginate

There are alginates and then there is fiber-reinforced alginate. This comes with greater tear strength and delayed shrinkage which makes it ideal for larger life castings as well as for special effects works.

Alginate is the material of choice for making body molds. This is a natural compound that is actually derived from seaweed and is used to make dental impressions. Its quick setting and skin safe properties make it suitable for using as the base material for life casting.

A variation of the regular alginate – with a slower set time than the dental formula – is used for making body molds. This alginate is mixed with water and the paste is applied directly on the skin. It sets quickly while capturing a perfect negative impression of the body part – be it face, hand, foot, torso, abdomen or even full body. A good quality alginate, when used properly, it will capture all the fine details and indentations of the body surface down to the fingerprints as well. Everything can then be reproduced in clear detail in the life cast.

Now alginate comes in different varieties to suit diverse requirements. The traditional formula is in the form of a white powder that contains silica and offers a firm set. Yet, it needs to be reinforced with a shell mold as the alginate will not be able to retain its shape on its own after demolding.

In case artists want to steer clear of silica formulas, there are silica-free alginates that offer a softer set and are, therefore, gentler on the skin. This is especially favored when making life casts of a baby’s hands or feet.

Both these categories of alginates come in variants of slow set, regular set and fast set, to suit varying dexterity and applications. For instance, the slower setting formulas prove to be very useful when making molds of the torso or other large body parts. The slower set ones are again preferred when working with infants.

The best type of alginate is the fiber-reinforced alginate – like FiberGel alginate. This contains fiber which not only helps enhance the tear resistance and strength, but also increases the alginate’s capacity to hold moisture. It also serves to delay the shrinkage of the alginate mold, thus giving more time for the casting process.

Therefore, FiberGel is the best choice for larger molds and actually, all life castings. In fact, FiberGel E F/X Grade Alginate (available on the EnvironMolds website, is specially formulated for professional high-production, high-end detailed E F/X work.

This FiberGel comes with a patent pending duo fiber matrix system that has been independently tested 40% stronger than the best options in the market.

What’s more, the fiber content also serves to prevent runs and drips. The alginate mix (when made using the prescribed ratio of powder and water) will stay where you put it. This makes it suitable for working on vertical surfaces too. The molds also stay soft and flexible far beyond normal alginates, thus extending the window for casting times without any loss of detail.

Correcting Mistakes in Plaster Life Casts

Errors are bound to happen at different stages of the body casting and life casting process. Here we take a look at the problems that can surface in a plaster life cast and how to correct some of them.

Life casting begins with capturing a mold of the human body and ends with a finished cast that is an exact reproduction of the model. The body mold is usually made using alginate or skin-safe silicone rubber while plaster is preferred for the life cast. The final piece is usually mounted and finished with a brass name plate.

Now there is a lot that can go wrong during the body casting and life casting process. While a lot has been written about working with alginate, let us take a look at the possible complications that can arise during the plaster casting:

Air bubbles – Like any other mold making or casting material, plaster also has a propensity to trap air that can show up as unsightly bubbles on the surface of the cast. Life casting artists are always advised to pour the plaster slowly and carefully in a thin stream from a corner of the mold. Tilting the plaster-filled body mold a bit or tapping the sides will also cause the trapped air to rise to the top and can be burst easily. However, if some bubbles still happen to appear on the life cast, they can be smoothed out with the thumb, back of a spoon or by applying some water. Some artists pop them gently with a knife and then fill the hole with more plaster. Rubbing with sandpaper will help level out the final cast.

Broken fingers – Features like nose and fingers are small and delicate when compared to the entire life cast. They are very likely to break during the demolding process – it could be that the plaster has not set enough or the artist has applied too much pressure or is working in a hasty manner. The broken part can be refastened by wetting both the edges and applying some plaster. Reposition the piece and hold it in place till it sets properly. The joint can be smoothed with a wet finger or some thin plaster.

Similarly, other distortions or squashed features can also be corrected with some careful resculpting. However, it is always better to make the corrections in the body mold itself as far as possible rather than risk disfiguring the life cast.

Rough surface of the casting – At times, the plaster surface of the casting may seem coarse and bumpy in places. This can happen due to various reasons like skewed ratio or improper mixing of the plaster. Either way, the best recourse it to smooth out the surface with sandpaper.

These techniques will work for minor errors and corrections. In case of a major blunder, it is better to redo the life cast rather than keep trying to correct an inherently flawed or inadequate piece.

And when the perfect piece is ready, it can be mounted on a marble or wooden base and finished with customized brass name plates engraved for that wonderful gallery finish!