‘lexicon’ definition
alginate is a flexible mouldmaking material used primarily in life casting. It is skin-friendly and fast-setting but very fragile (compared to silicone) and normally has to be used immediately to make just one casting in plaster. See ‘Casting polyurethane resin into alginate’ November 9th 2012
longer summary
Skin friendly, very fast-setting (using it effectively takes practise), usually comes as a powder to be mixed with water, significantly cheaper than silicone by mixed volume (as much as a third of the price when mixed ‘pourable’ i.e. with twice its volume in water), used mostly for life casting tasks. Moulds do not last, very limited flexibility, normally only plaster or wax casting recommended (but see above post for using polyurethane resin). Some brands are white, others are artificially coloured. Mixing/working guide 1:1 with water by volume to make a paste, 1:2 with water by volume to make a pourable liquid. At 1:2 ratio 100ml (settled) of powder will yield 200ml pourable mix. Average cost £10 per 500g packet
davidneat 