Chavant NSP (which stands for 'Non-Sulphur Plasteline') is a wax-based clay which doesn't dry out or shrink, making it ideal for sculpting a variety of things such as prosthetics which require feather thin edges.
The 'Non-Sulphur' part is an indication that it is suitable to use with platinum silicone moulds and appliances. Sulphur had in the past been present in some wax-based clays but can affect the setting of platinum silicones used extensively in prosthetic makeup and effects.
Chavant NSP is available in two colours (brown and green). They are the same material; the colour choice is a personal preference. It is also available in three grades of firmness: 'Soft, 'Medium' and 'Hard'. As it is wax-based, it will temporarily soften with heat and will return to its original firmness when cool.
Most people opt for the 'Medium' as a general-purpose grade. Why are there soft and hard versions I hear you ask...? Well, if the ambient temperature of where you are working is particularly cool, then 'Soft' may be a sensible choice, as a harder firmness may be difficult to manipulate in that temperature. Likewise, should you be in a very warm climate, then the 'Hard' may be better as it wouldn't soften too much in the heat. A hairdryer can be used to temporarily soften the plasteline, and 'plumbers freeze spray' can likewise be used to quickly chill and harden it if needed.
Sculpting appliances on lifecasts and cores is typically done by building up small blobs of plasteline on the surface and blending them together to create the necessary form bit by bit. 'Medium' softness is usually soft enough to manipulate by hand at first, and then refine shapes and textures using sculpting tools.
How to use it
Chavant NSP can also be melted in a double boiler or pan on a low heat, although many use a dedicated electric slow cooker/crockpot on a low heat setting. Once molten, the liquid plasteline can be brushed onto cores to quickly build up larger areas. It can also be swilled and cast into silicone and alginate moulds to create sculptable casts once cool.
This is a great method for making limbs and heads, filling lifecasts with plasteline instead of plaster which allows rigid moulds to be made of them, or sculpting the eyes open on a head for example.
A lifecast can be swilled with a few layers of molten Chavant NSP, allowed to cool and then be filled with a rigid foam such as POLYTEK R8 which will expand and solidify, creating a lightweight limb which has a plasteline skin you can sculpt and modify.
The great thing about wax-based clays is that they can be reused. One way this can be done is by melting it back into liquid form. Even if bits of moulds, clay or other mess make it into the recycled plasteline, you can strain the molten NSP through a metal sieve, kept specially for such a use.
BONUS TIP: We like to pour the molten plasteline into flexible ice cube trays. When it cools, you can pop out the smaller pieces as you need them in the future. Make sure you pour the molten plasteline over a clean work surface so any accidental spills can be scraped up and reused once cool and solidified.
Chavant 'NSP' and Monster Makers 'Monster Clay' are both wax-based plastelines used to sculpt appliances, maquettes and props. So how to choose between them?
Both come in three different types of softness, can be melted with heat and reused multiple times making it an economical material. The main differences are in how they feel to sculpt with.
Chavant NSP is a stickier wax-based clay which tends to be easier to build up appliances if that is how you like to sculpt - gradually building up a bit at a time. Some sculptors prefer to apply too much and carve back for example, and Monster Clay tends to suit this method a little better.
Monster Clay is a relatively newer material and feels less sticky to the touch, but does bond well to itself and is cleaner to use as it doesn't cling to tools so much. This makes it easier to create crisp, clean lines and burnish smooth finishes. Some people prefer this cleaner feel of working as it s less 'bitty' when shaving down.
The slight stickiness of Chavant NSP is preferable to some as it makes building up sculptures quicker, especially for thinner appliances and when blending out fine prosthetic edges.
When melted, Monster Clay liquifies beautifully into a smooth creamy fluid, making it excellent for swilling into moulds. Chavant NSP does melt to a liquid, but doesn't flow quite so well as Monster Clay in the same conditions.
Monster Clay does feel firmer to the touch compared to Chavant NSP, so depending on your finger strength and the ambient temperature of where you work you may find Monster Clay a tad firm if you prefer softer clays. In terms of firmness, Chavant's NSP Medium feels similar to the Monster Clay Soft.
Both are excellent clays for sculpting with, the choice of which to use depends on how they feel in the hand. Choosing a clay that feels right to you is important, as you will likely spend a lot of time handling and shaping it. There isn't a 'right or wrong' material - just what feels right to you.
When using any products, materials or equipment, you should familiarise yourself with them and take appropriate health and safety measures to protect yourself and others around you from harm. Obtain and consult the relevant MSDS (Material Safety Data Sheet) from your supplier. Once melted, Chavant becomes liquid so take sensible precautions to avoid injury, use personal protection equipment and correct workwear to minimise risk.