mixing plaster and structolite?

I don't worry about using any recommended ratios. I mix it differently depending on the use.

For making rock castings, I mix the plaster on the soupy side. I use fast-setting plaster of Paris for rock castings.

For creating a hardshell for mountains, etc., I use Structolite and mix it more on the stiff side. The stiffer it is, the more rock-like texture you get from the Structolite. I'll adjust mixes based on this fact and the type of landforms I'm working on.

IMO only those individuals doing critical casting of parts, such as for those excellent Hydrocal building kits, have to worry about ratios and maximum strength.

For the rest of us, the materials are very forgiving.

Jim

Hydrostone calls for a 3:1 ratio (Plaster to water). Like Jim, I adjust it depending on what I'm doing. At that ratio it's like loose pancake batter.

There's a set ratio you're supposed to use? I'll be dog!

I use probably 95% Structolite and mix it until it looks like pancake batter.  If it's too soupy add a little more Structolite.  If it's too dry add a little more water.  You be the judge on how you want it.

TIP!  After you've mixed it to your desired thickness let it slack (rest) for about 5 minutes then mix it again.  This will make sure you don't end up with any dry lumps.   

Go onto USG's website and there's instructions on mixing every one of their products. That's where I found it.

Where do you purchase Structolite?

The local Home Depot has Structolite in 50 lb bags for about $11 a bag. In this store it is located in the drywall products section, not with the plaster in the paint department.

Jim

Corner mountain made with structolite and plaster rock castings.

Mixing plaster depends on the manufacture's product it all varies, so you have to read the instructions! Something us engineers are not good at.

I had a thread going about this and there is a small learning curve in making the right mix, how much, and you need to pour before things set up. Also do not add water after the initial mix... My first batch I had a perfect cast part of a 1/2 gallon bucket.

OK, thanks. I have looked at Structolite in 50 lb bags at Home Depot.  Is the the powdered plaster in the paint department useful for molding rocks or making mountains.

The plaster in the paint department is usually plaster-of-Paris. Its fast setting time and smooth finish makes it great for castings.

However, that fast setting time makes it inconvenient for general mountain/hardshell work. The very long setting time of the Structolite means you can mix a big batch and work all evening without worrying about it setting up. Plus, its texture gives it a rock-like appearance

Jim

Part of the insanity is the tools. These tools are designed for premixed drywall compounds but work well, IMO.  I haven't done a lot of major mountain building but for skim coats, feathering edges, adjusting grades  most any wall or floor compound material will work.





This 1/2" elevation difference is feather-in with a few coats of compound and sanding.





More expensive ground cover materials are used to a minimum after the grades are adjusting with most any plaster/filler compound.

Looks good! Thanks for the pictures.