Casting building walls

Hi Rod

Which material depends on the effect you are trying to achieve. I also am just learning. I just bought a kit from MicroMark, which contains everything you need to get started. It retails for around $99.

I originally started with an Alumilite kit from Hobby Lobby, but found it difficult to use. The MicroMark stuff is mixed on a 1:1 ratio, and should be easier than the 1:10 ratio Alumilite uses. From what I have read, the MicroMark is also more durable.

Smooth-On Products

The best ,

The quality of the silicone is key , trial kits around $30

As noted above, it depends on what effects and types of walls you are casting.

Traditionally, brick and stone tends to be done in hydrocal or related plaster like products.

All can be done in resin.

I started in casting in resin using the Smooth-on products and wandered about to the Alumilite products (and Micro Mark) and found all to be self-limiting in ease of use and in options of working time.  Working time is important when you are pouring larger amounts of resin (O scale cars bodies...) as you do not want to be rushed about with a 3 minute resin that's setting up in your mixing cup as you are 1/2 way through the process.  I do still use one of the RTV products from Alumilite for some specific types of molds that suffer from significant undercuts.

I have for the present time settled on the Miapoxy products:

http://www.miapoxy.com/

which were (and still are as the bottles are labeled as Freeman) actually the products from Freeman Manufacturing & Supply Company which is a real resin company standing behind the hobbyist products. 

They have a lot of teaching videos available on their web site as well.

I just bought the Aluminite starter kit today. I need to cast some figurine accessories that will quite small and would be a pain to make all the duplicates by hand so I'm sure that the short working time of the Alumilite resin won't cause a problem. I'd like also to use their silicone to make plaster molds. I've used the latex plaster molds and find that process to be excruciatingly slow...days and days and layer by layer. For larger projects, I will use the advice you gave for different materials.

Should not be a problem providing you let the plaster adequately cure before attempting to demold.  I've used the same molds interchangeably for hydrocal and resin.

You drop a hydrocal piece and you almost certainly break it. Zero flexibility. Resin is much more forgiving when mishandled. More flexible.

Resin generally weighs less by volume.

Large hydrocal pieces (say 12 X 24 inches) are best cut very slowly with a hsnd saw to prevent chipping/breakage.

Resin can be easily cut with care on a radial arm saw with a 160-200 tooth blade.

Hydrocal can be easily repaired using spackling paste.

I have used both resin and hydrocal for large building fronts and am happy with both, but my preference would be resin.

Unless it was stone, I'm with the resin option, too. 

Anyone ever try Durhams Water Putty?

Doesn't it have a slight amount of shrinkage as it hardens?  I recall trying someones water putty, and it shrank just a tiny bit and cracked, at least for me.  Maybe I didn't use it correctly.