Board logo

Mould plaster
joolsmi16 - 9/2/06 at 06:02 PM

Hi all just had delivery of a bag of Herculite plaster to finish my mould has anyone any hints/tips that may make things easier?

One worry I have is that I have used foam from a local supplier that I cut to size and fitted will absorb the water from the plaster and crack it once dried?

Also do I need to spray the finished mould with anything to protect it, unsure at the moment if I am going to do the fibreglass.

Cheers

suparuss - 9/2/06 at 06:18 PM

never heard of herculite, but dont forget that most foams react to polyester resin so make sure you seal it with pva and/or epoxy resin before taking a mould.
to finish also youll need several coats of release wax and also pva release agent is agood idea for the first few pullls.


russ.

nitram38 - 9/2/06 at 07:19 PM

quote:
Originally posted by suparuss
never heard of herculite, but dont forget that most foams react to polyester resin so make sure you seal it with pva and/or epoxy resin before taking a mould.
to finish also youll need several coats of release wax and also pva release agent is agood idea for the first few pullls.


russ.


Polyester resins can be used on most foams as most foams are styrene based.
If you have bought polyurathane based foams (which are much dearer) you can use styrene based resins/car body filler.
If you use products that are alike, then they will melt each other.
In other words if you use styrene on styrene foam, it will melt.
Polyester products are dearer than styrene so you will need to decide what you what to be more expensive based on quantities. Styrene Foam with Polyester resin or Polyurethane Foam and styrene resin.

Regards Nitram

Hugh Paterson - 9/2/06 at 07:49 PM

Use closed cell foam, it absorps tiny amounts of H20 (unlike the poly). Try and find a bulders merchant that stocks the blue cavity wall foam in blocks, from experience they are the cheapest source. Buy from a GRP supplier and it usually costs more. Unless of course you are purchasing trade in bulk! Herculite is good for one of plug and buck manufacture, I take it you doing somthing small? MDF baseboards and a combination of poly filler foam block and sprayed with a high build primer and gloss finish are usual for anything over 2-3M Sq. If you are doing a one off "pull" from your buck/plug a hard wax polish and sprayed with PVA would be quite straight forward. u2u me if u get Stuck (no pun intended)
Shug.