rock background mold idea

[serjuanca888]

I have been looking into making an in tank 3-D background. I have researched everything: foam, fiberglass, concrete.

I would like to make a mold out of real rocks. I was thinking about lying a bunch of rocks the way I wanted my background to look. Then I want to pour plaster of paris over them to make a mold. Then when the mold dries I would cover the it with expanding foam. Then epoxy the foam. Does this idea have any flaws? Any ideas to improve it?

[Matak]

Just be sure you use aquarium safe epoxy.

[125gJoe]

Look at this link!

Cave Background (http://www.duboisi.com/diy/BNdiygrotto/bndiygrotto.htm)

[RENEGADE]

i was looking for that link thanx 80gjoe

[serjuanca888]

Does anyone know anything about using plaster of paris to make molds? Do you know anything about a release agent?

What about foam? Will the spray can type work? or should I get the two part hand mix type? I also heard about something about latex foam from Great Stuff. Anyone know about that?

[125gJoe]

Originally posted by RENEGADE
i was looking for that link thanx 80gjoe No prob... :)
I liked the idea, but I'd bring the bottom of it out some - towards the middle some, not much. That would give it more 'depth' perception and look more natural. Maybe even bring out a top corner too, rather than just a verticle 'wall'.

[carpguy]

You should visit this site (http://www.sculpt.com/) and do a little research into some of the products they list in the casting section. Call 'em up and ask a few questions (be aware that they're a real store, not a phone bank… they do get busy, and they absolutely know what they're talking about).

The nutshell rendition is this… you don't want to make a mold of irregularly shaped objects with a rigid material like plaster. You can get rubbery casting agents (http://www.sculpt.com/catalog_98/RUBBERS/RUBBERINDEX.htm) that will deform when it comes time to peel them away and still hold their shape.

And if you're not looking to go back and sculpt later I'd take a pass on the foam as well. I'm in the planning stages of a similar project and am experimenting with grout (a type of cement that comes in fairly small bags, tinted all sorts of nice natural looking colors). I'd also looked at quick-curing concrete, which I've seen used to get a very natural look.

If weight is an issue, you can build up a shell of grout/concrete in the mold and then fill the back with something like Great Stuff (http://www.dow.com/greatstuff/products/index.htm).

An idea that I had for a background was to go hunt down an actual suitable rock face (we've got lots of them around these parts) and take a mold off that. That site also sells a type of wax that can be used to build dams to hold the molding agents that can be setup in place and removed without harming the area.

HTH

[serjuanca888]

I started my mold today with the P of P. Weeeeeeeeeell, it turned out it would cost me more than using expanding foam. So I am just going to use the foam as it is easier, cleaner, and doesnt make me light headed.

[seeseven]

I've made plenty of molds using plaster and expanding foam ...be it 2 part foam or the stuff you get in cans from hardware store....first tip is build a box for your casting coz when you get to the stage of spraying the foam or pouring it depending on what you use you want the foam to be trapped so it compresses more and makes a better mold if you dont you'll get alot of gaps between the foam and the plaster.....dont forget to use a release agent on the plaster or you'll never get the foam off in one peice ...there are heaps of different release agents but if you wanna go the cheap way get a can of spray oil from the cooking section in your local supermarket and spray the plaster with it .....when you pour your plaster make sure you bang the box with a hammer lightly so the air bubbles can rise ....if you dont when you pour or spay your foam the pressure of the foam will crack you plater mould in two.....i could go on an on ....any question just ask.

[Rocketman]

Now I can't remember who posted this link, (maybe you or someone you know, Joe?) but maybe 7 or 8 months ago someone posted a link to a tank they had which featured an awesome 3-D Waterful background. Around the same time, (maybe this was the same project, actually,) someone else came up with an idea to take mesh and attach Java Moss to it. It came out quite nicely, although seemed very labor intensive.