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[TK 109]

has anyone tried this? i know you can mix concrete and plaster together to make a strong plaster mold, but what if you just cast a piece in JUST concrete (quickcrete)? it would be heavy, and imagine you would have to fill and sand some spots, but would it last longer than plaster? i'm trying to find a local place for casting materials, i heard plaster is ok, but dries and cracks after a while, hydro(a?)-cal is good stuff, but not local, and some people mix plaster and concrete to get a stronger mold.

what do you think? any advise/input would be very helpful.
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-Alex

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[PARATECH1]

Don't use concrete at all. Use cement. Concrete has rocks and cement does not. If you use cement just simply use S-Type masonry cement. It's easily found at any hardware store that sells cement or concrete. S-Type masonry cement is a mixture of portland cement, lime and sand. It comes in 60 to 90 pound bags and is usually under $5.00 a bag. To make your molds as hard as possible use as little water as possible. Look for a liquid concrete / cement hardener additive where you purchase your cement. Use this instead of water. Your mold will be way harder than a cement / water mixture.

Some hardware stores carry hydrolic cement. It has all the above ingredients of the masonry mix including a powder form of the hardener additive. The only thing is that you still have to add water. If you can't find the liquid hardener you may try using this type of cement.

To help in getting surface bubbles out use on of those cheapo type black sponge brushes with the handle. Once you have the form you want dip the brush "TIP" in water and go over the surface to smooth everything out how you want. A regular type brush will leave surface marks like a broom stroked concrete slab. Don't apply to much water at one time to the sponge.

If you make your cement mold on a table or wood use cheap plastic (grocery store bag) underneath the cement. It will be easier to remove without sicking and chipping your mold edges.

[jegner]

Good tips, and I'll add that Rockite is a great 'anchoring cement', is actually a gypsum based material. A little harder to find, but smaller hardware stores usually stock it. Lowes and Home Depot DO NOT.

I've 'cut' rockite with Plaster with limited success.

Jim