Plaster Casting

[Barewolf]

Hi Guys,

I'm working on making casts of various things i'm making from Clay. Ive made my Silicone mould and I'm torn between casting in Polyeurethane or Herculite Plaster. Polyeurethane is very expensive based on the size of what i'm casting, so I thought if I casted them in plaster it would be more cost effective, however...

These casts will be outdoors and i'm not convinced Herculite will stand upto the elements, so is it possible that there is something liquid that i can paint over it, that will keep the detail, yet harden to give a protective barrier like plastic? Preferably something that will not be opaque, as i'd like to paint the cast first.

Would perhaps polyeurethane do this if i got the translucent variety?

[Osem]

What about PVA?

http://www.diydoctor.org.uk/projects/pvaadhesive.htm

[Barewolf]

maybe but im not convinced PVA will withstand that much of the elements, few hot days and it would probably burn it off.

[Taf]

Plaster for outdoors? Why not concrete?

[Barewolf]

Originally Posted by Taf

Plaster for outdoors? Why not concrete?

Because they are ornaments im making in clay first then making a master mould, concrete wouldnt give the detail, thats why it has to be resin or plaster as they bring out the details.

[Osem]

Originally Posted by Barewolf

maybe but im not convinced PVA will withstand that much of the elements, few hot days and it would probably burn it off.

I was thinking more about mixing the PVA in with the plaster than just coating the ornaments with it.

http://olivierduhamel.hubpages.com/h...for-moldmakers

[Taf]

Originally Posted by Barewolf

Because they are ornaments im making in clay first then making a master mould, concrete wouldnt give the detail, thats why it has to be resin or plaster as they bring out the details.

A neighbour and friend makes excellent concrete statues and things like planting troughs. Great detail too, it all depends on the mould I think. He did tell me that you have to let the concrete "age" to purge any moisture or they will crack during the first frosts.