Alginate Plaster 1KG

Code 8022

Alginate (pronounced al’jinate) is a flexible mould- and impression-making material; a gel is formed by mixing the alginate powder with water; it is sometimes referred to as ‘chromatic alginate’, because it changes colour according to the phase it has reached after mixing. The material is widely used in reproducing decorative work, small to medium-size objects, figurines, etc. and patterns or mouldings in plaster and timber, particularly in restoration work. Alginate is completely safe in direct contact with skin (the same material is used for making dental impressions) and it sets very rapidly, so it is also the preferred material for life casting (making moulds of the face, body, feet and hands, etc.). Both types of work are explained in more detail lower down this page.

Alginate powder is usually supplied in a foil sachet; it is manufactured from kelp – a variety of seaweed. In common with latex and silicone, it reproduces an extremely accurate impression – capturing such detail as the pores of the skin. Alginate has several advantages over silicone and latex:-

i) It sets very quickly and can be separated from the subject within 3 to 4 minutes of application.

ii) It is clean, economic, easy to apply and needs no special skill or tools, additives, etc.

iii) No release agent is required against non-porous surfaces, the mould detaches from the original as it sets – although vaseline should be applied to avoid trapping strong hair growth, cloth fibres, etc. when used in life-casting, and a sealer such as shellac should be used to seal porous surfaces, e.g. clay, card, etc.

Its drawbacks are:-

i) It is quite a floppy material once set and large, unsupported areas tend to sag and sometimes tear*; this often dictates the method used to make the mould. *Serious tears can be repaired with superglue.

ii) Alginate moulds are not particularly durable, and need using within 24 – 48 hours unless kept in humid conditions; however, using the mould soon after forming doesn’t normally present any problems.