Release agents & impregnating agents for moulding & casting of sculptures & objects

Before choosing a release agent: what and with what exactly do you want to mould and cast?

The decision for one or more release agents is made when it is clear which object you want to mould with which impression material and with which material you will make the cast. Important for the choice of release agent is:

- what is the original model, the object to be moulded, made of?
- what surface structure does the master model have? Is it coloured?
- is the master model particularly valuable and must therefore be treated particularly carefully?
- with which moulding compound do you want to mould?
- with which casting compound do you want to make the cast?

Accordingly, you will choose the release agent and, if necessary, an impregnation. Basically, original model, moulding compound and casting compound should match . The aim is of course also to ensure that the master model is not damaged during the moulding process.

As a general rule, we recommend that you first test the release agent or impregnating agent on an inconspicuous area, e.g. on the back or underside of the master model, before applying it over a large area to ensure that there are no undesirable reactions with the surface. It is not always possible to accurately determine the nature of an object from a mere view.

What are the different types of release agents?

Release agents and Impregnating agents can be characterised in different ways in terms of specific functions.

For example, release agents are water-based, solvent-based release agents and oil-based release agentsl – some release agents also fall into several categories. Not every release agent is therefore suitable for every substrate or for every moulding or casting compound. The components usually also determine whether and how well the release agent can be removed again or whether it remains, for example, as a permanent protective layer.

In addition, release agents differ in how they are applied: e.g. with a cloth, brush and brush or as a spray. Some release agents needto be heated first so that they can be applied.

If you have a master model with a detailed surface, for example, it is advisable to use a release agent that is very finely sprayed on so that no detail is lost.

If, on the other hand, a surface to be moulded is porous, has cracks or a rough texture, a pre-treatment with a supporting, filling or levelling agent may be advisable, if not necessary.

When does my master model or object that I want to mould need pre-treatment or impregnation?

Some original objects require pre-treatment or impregnation before they are allowed to come into contact with a release agent or the impression material. The aim of the pre-treatment is to close  and protect the surface of the original object, i.e. to provide it with an impregnation so that neither the release agent nor the impression material can penetrate the surface and adhere or damage the object. The original object should look exactly the same after moulding!

Basically, two types of agents can be distinguished for sealing surfaces: There are agents that are water-soluble and can be

washed off again, and agents that remain on the object but are virtually not visible. This can be a lasting protection for the object, even against normal environmental influences.

With valuable and/or sensitive original objects very careful consideration should be given to what is "reasonable" for the object. Can it be washed off without problems? Does it alter the object if it is coated with a thin layer of wax or another transparent film, even if this can hardly or not at all be seen? Does the release or impregnating agent contain asolvent that could attack the surface of my master model? Or does the impregnating agent react in some other way with the surface of my object?

Pre-treatment is recommended, for example, for rough, unpainted wood, especially if it has cracks, for objects made of unpainted plywood or pressboard, for objects made of unglazed ceramics, of cement, concrete, plaster or stone, generally for allabsorbent materials or materials with open structure (e.g. Ytong, brick, sandstone etc.). Pre-treatment may also be useful on original objects that have been painted with
water-soluble paints or paints that are not solvent resistant.

If an object has cracks or an uneven or rough surface, pre-treatment is also advisable, as otherwise the moulding compound can settle in the cavities and the mould that has become solid cannot be removed well. Cracks in wood must therefore be filled, a surface with many air bubbles may need to be evened out. This may mean that in some objects mainly the shape can be removed, but not the original surface structure.

Pre-treatment is not usually necessary for objects made of solid, smooth materials such as glass, porcelain, glazed ceramics, metal and plastic or for painted objects. When taking an impression with silicone without a release agent, however, a metal surface, for example, can also oxidise. In this case, e.g. a release wax is recommended as an impregnation. In many cases, the impregnation then also serves as a release agent.

Which agents are suitable for pretreatment or impregnation?

At this point, we will only mention a few agents that can be used for the pre-treatment of original models. For more information, please refer to the respective products!

PVA (polyvinyl alcohol): seals open-pored surfaces such as plaster and wood; is water-soluble, can be easily washed off objects that tolerate water. If the surface structure of the object is very porous, the PVA layer can be removed again by sanding if necessary. PVA is not necessarily suitable if another release agent or a water-based impression material is to be used, as the agent could be dissolved in the working process.
Water-based varnish: A matt water-based varnish can protect e.g. untreated or coloured wood surfaces. Water or water-based release agents and moulding compounds can then no longer penetrate.

Removing soap: can be used, for example, to level out cracks or a very rough surface; is water-soluble and thus washable from objects to which water cannot harm.

Removing wax: can also be used very well to fill in cracks or rough surfaces; also makes the surface insensitive to water. Accordingly, release wax can only be removed – to a limited extent, e.g. with hot water or suitable solvents, provided the master model allows such treatment. On the other hand, release wax can also providelonger-term protection.

Moulding: Which release agent do I use for which materials?

Plaster from plaster: To separate plaster from plaster, you can use a wide variety of very simple release agents, such as washing-up liquid, soap, Vaseline or clay slip (clay dissolved in water). 

Making casting moulds from silicone: Almost all release agents offered at bildhau are suitable for separating the master model and silicone, if a release agent is required at all, depending on the nature of the master model (pre-treatment may be necessary, see section above). Please note that a release agent containing oil or grease (e.g. Vaseline, demoulding grease, silicone mould release cream) may impair the curing properties of two-component silicone and should therefore not be used in this case. If you want to mould an object made of metal with silicone, we recommend using e.g. a release wax as a release agent, as the metal can oxidise when it comes into direct contact with the silicone. Undried clay, plasticine and wax as master models do not usually require a release agent when making silicone moulds. 

Silicone from silicone: If you are working with multi-part silicone moulds, they must be separated from each other during manufacture. For this purpose, you need a release agent such as Universal Release Wax Z 25, PST-4 or ARTIDEE Silicone Mould Release Cream. Please also note here that a release agent containing oil or grease (e.g. Vaseline, demoulding grease, silicone mould release cream) may impair the curing properties of two-component silicone.

Manufacture of casting moulds from synthetic resins (polyester, polyurethane, epoxy): For the manufacture of casting moulds from synthetic resins, PVA, Universal Release Wax Z 25, PST-4 or ARTIDEE Mould Release Agent is suitable for separating from the master model.
For further information on the functions of the individual release agents, please refer to the respective products!

Pouring: Which release agent do I use for which materials?

If you want to make a cast in a mould made before you, the choice of release agent depends on what your mould is made of and with which casting compound you want to make the cast:

Silicone moulds: If a silicone mould is to be poured with cement or concrete, a grease-containing release agent is required, especially to protect the mould from the aggressive casting compound. For plaster casting in a silicone mould, a release agent is usually not necessary, but can be helpful for easier demoulding of more complicated moulds (e.g. ARTIDEE mould release spray). For casting with artificial resins (polyester, polyurethane, epoxy) in a silicone mould, you can use e.g. PVA or ARTIDEE Mould Release Agent.

Synthetic resin moulds (polyurethane, polyester and epoxy with glass fibre): In principle, synthetic resin moulds can be poured with all casting compounds, only casting with liquid clay is not recommended, as the water cannot escape from the clay – plaster moulds are much better suited here. PVA or the ARTIDEE mould release agent, for example, is suitable as a release agent. If you use PVA as a release agent, please always make sure that you apply the PVA in several layers and that each layer is completely dry before you add the next layer. PU moulds, but also other plastic moulds, can be processed very well with release wax (e.g. ARTIDEE Mould Release Wax) or other wax-containing release agents (e.g. Universal Release Wax Z 25 or PST-4). When moulding filigree objects, please make sure that the wax layer does not become too thick – so details can be hidden.

Latex moulds: Can be used for almost all casting compounds: For ceramic casting compounds, gypsum and cement no release agent is required. However, release agents may facilitate demoulding depending on the design of the mould, e.g. ARTIDEE Mould Release Wax, ARTIDEE Silicone Release Lacquer Spray, ARTIDEE Mould Release Agent. Cement and Concrete may attack the latex. If you are planning multiple casts, a greasy release agent is recommended to protect the latex mould. Also artificial resins attack the natural product latex. Here, a release agent is required to protect the mouldn, e.g. ARTIDEE Mould Release Agent or ARTIDEE Silicone Release Spray, if you want to cast with polyester or polyurethane. To prevent latex moulds from sticking together, it is best to rub them with talcum powder.

There are very many different combinations of moulds and casting compounds. We can only list a few possibilities for the use of release agents here. Therefore, please also refer to the individual product pages or contact us if you have any questions about your specific project!