Resin Addict Forum

No reason you can't pressure cast with plaster (that I know of). My main concern would be the details breaking too easily during demoulding.

Here are the photos o the 7 objects :

Base 1 and chocolate top (assembled approx 28mm high)


Base 2 and shield 1 (assembled approx 28mm high)


Base 2 and shield 2 (assembled approx 28mm high)


Base 2 and shield 3 (assembled approx 28mm high)


Lutèce trophy (approx 28mm high)

I finally bought some smooth on resin "Task 8" which is specially designed to resist 130°C !

Perfect !

Nice trophies!

Hi To all

Thought i just add a few comments here with some of my experiences with soft masters for the making of spin casting molds. I usually choose the safe way and make a RTV mould of the figure then spin cast. I use Dow Corning 3120 , reliable rubber , Very messey stuff and stains all things known to man ,once set, it makes a pretty good mould but not the best rubber if you have under cuts. There are other rubbers available from Barns and others which i am sure work just as good.

If however you want to valcanize the masters straight into silicone of black organic valcanizing rubbers at 150 oC or sil at 180 oC Could be risky. Many years ago I valcanized a small train carriage side frame that was cast in a resin UC 30 and all valcanized ok and produced good white metal castings . This was just to try to see what would happen to the pattern .The resin master came out a smokey grey after the valcanizing and was a bit brittle . Have used timber masters and worked well. Timber crushed to pieces but made a good mould with excellent timber grain detail.
Recently I valcanized a pattern from a rapidprototype I was given of a engagment ring.
This was valcanized at 150 oC for a hour in organic rubber , all the detail came out ok but the master was affected by the heat and broke to pieces after. If I had paid big money for a rapidprototype pattern I don't think I would be risking it in the valc press.
There may be a possible alternitive as I have read on a web site of a rubber for spin casting that valcanizes at 90 oC from dizzy rubber . com Expensive to get a sample as I have to by a box of 10 sets ..(Any one want to share) Would be interesting if this rubber could be used for rapidprototype patterns or other fragile materials. But as for the work I do now for fragile items its all RTV rubber.

Johncast
orncastings.com