I've made a few recents posts with regards to making gypsum plaster sculptures and other sculptures...i'm still fairly new to working with plaster. I'm currently using Crystacal R. When sanding sculptures down I've found alot of chalky marks that keep coming off from the plaster onto fingers when handled. I can't sell the sculptures if this happens as customers are just going to pick the figurine up and end up with plaster marks on their hands and wonder why it's rubbing of. Apart from obviously sealing plaster with a varnish is there any other way to prevent it rubbing off on your fingers? Is sand papers the best to use or is there an alternative method?

Many thanks for your reply. Do you recommend a sealer? Ideally looking for a paint on sealer. One of my issues is I have a specific sculpture with figurine that incorporates a small sunken hole whereby a small tea light candle is placed into it. If I used a sealer would this be affected in any way say by the heat given off from the candle. This is one of my main concerns as I understand tea light holders might normally be made of something stronger but I can really only use plaster for my requirements.

When I worked in the ceramics industry, we used Crystacal R for models and prototypes. For manufacture, the masters were "sized" with soft soap, which prevented the plaster moulds sticking to the masters. For prototyping, the plaster was resin impregnated. The model was put in an oven to thoroughly dry, then PU resin was mixed then painted onto the surface, which soaked into the plaster. The model was saturated in resin, then the excess wiped off and then it was returned to the oven to fully cure. Because the plaster was impregnated with resin in this manner, we were able to spray with paint and polish to a very high gloss finish.

You can do a similar impregnation with polyurethane varnish, but it must be thinned for the plaster to absorb it and the plaster must be bone dry...

Ive not used shellac for years, but I remember it going a brownish colour, as it ages....? Or maybe that was just an old batch!

thanks for the replies guys. I'm going to do a few test tommorrow with a couple of different varnishes I have.

One further question if you don't mind answering with regards to strength and colour of plasters...

I have been using crystacal R so far to make a few sample casts. The casts come out fine with a few air bubbles in places but as soon as removing from mold I run my fingers over the bubbles and it seems to do the trick as they fill in nicely. The only issue is the areas where the bubbles were seem to change colour slightly once the cast has dried so you get small rounded patterns of a different shade within the bright white cast. This isn't a massive issue but I just wondered if there was a different plaster that is either the same strength or harder than crystcal R but might produce a slight off white colour once set as opposed to just bright white?

Would crystcast be any better or something like herculite 2 in terms of being not such a bright white and also as strong or harder than crystacal R? I think I've read that herculite 2 was not as strong but the finish is not so much of a bright white. The item I'm making is a very simple cylindrical sculpture with approx diamter of 11cm x 4cm height. The stronger the plaster the better just to avoid being easily scratched or scuffed but ideally require a reasonably quick demolding and setting time.

If anyone can give some clarity on the best plaster to use it would be greatly appreciated.

You could try Molda 3 Bis. That dries to an off white colour and has a good strength, but is a little gritty for cleanup. We used to mix it 50-50 with Crystacal R. The discolouration is due to when the plaster is poured and could indicate a late pour where the plaster has started to set...

thanks for the replies guys...

Just one further question and slightly randon but is there any suitable way of applying satin ribbon around a plaster base? For example I have a round base approx 4cm high and It always seems to get more airbubbles o the sides more than anywhere else. I can smooth out the sides with my finger but it still leaves a few small bubbles that look a little unsightly. I've thought of an idea that would actually suit the base area and hide bubbles from sight. Because the item in question is a decorative gift sculpture and I can place a satin ribbon around the base.

My issue is using double sided tape to apply ribbon won't really adhere to the plaster for long term use. The only idea is using glue and in particular I find UHU glue very good for plaster such as crystcal R. However, if applying this under the ribbon surely the glue is going to show through in places and I'm going to end up with blobs of visible glue showing through. Is there anyway of applying something like a satin ribbon without any glue showing through it?

you could try hot glue on the end, wrap it round, then another blob of glue to fix it......