Hi all,
I've followed the Quickwall thread and the stepping stone threads and the hypertufa threads and love all that a LOT, but I was wondering if anyone works at all with silicone molds. I love sculpture and would love to make molds to cast things. I've been trying to get a handle on what a good structural concrete mix would be to use. There's a lot out there on the net, but I was hoping somebody here had first hand experience who I could ask questions.

Any thoughts?

Tabby, not me but hopefully someone will come along and offer you some help in this area.

Seems like I saw a bunch of videos of that on YouTube...I can't really remember where or much else, but they made silicon molds of architectural details and ornate plaster and later built forms around the molds and filled them with wire & rebar and then concrete...

I can't find what I was looking for on YouTube, but these will give you some good ideas. Lookie around at all of the links on the right hand side of the YouTube page and see if these might be more along the lines of what you are looking for. I know that you can get a whole lot more detail with the silicon molds. They are used to replicate ornate plaster...
Making molds for a concrete fence: http://www.youtube.com/watch?v...

Tabby... well the fibered concrete is good .. it has fibers to prevent cracking... what we need to know is what you're planning on casting.. size and such... larger castings would need wire... rod... metal screening... chicken wire or any number of metal types to have inside the casting.. wheather it will be used in any way that would require structural strength to your finished concrete piece..

Small castings probably 10 inches high at most and thick enough to support themselves, such as gnomes, critters, etc.

yes.. lots of cut outs and under cuts in a figure.. sounds like it would have to be a two piece silicone mold ..and being short and thick the fibered cement should do well.. even without added steel although a metal stake in it and sticking out the bottom would help them to stand upright..

I've made a bunch of patio blocks but maybe that's not what you're asking. However, the mix I used was soil cement, with about three parts of my native sandy soil sieved to remove larger bits, two parts Portland Cement. They worked out great, and I used styrofoam blueboard to make the molds out of:

Here's what it looks like finished:




You can see more about how I made them here; http://www.bluefoxfarm.com/pat...

Those are really cool!

Very nice Jackie!

The typical concrete mix is 1-2-3, 1 part cement, 2 parts sand, 3 parts stone. In your case, 2 parts Portland cement, 2 parts builders sand, 1 part small small stone. also a handful of long fiber fiberglass. Mix well. Water is the most critical part. Start small and slowly add until you get a bread dough consistency. In a water proof mold, you may need to have a very dry mix. Start small and experiment. The basic concrete mix is not what you want here.

It will be the test in the spring to see if they made it through without cracking (or crumbling). It's all an experiment...