joint compound or plaster of paris


B

BIG DOG

Member
I actually met a guy the other day at hobby lobby who's into trains He says he likes joint compound (the redi made kind) over plaster of paris, so I thought I'd try some with some styrophome(sp) as he said do it. Here's what I noticed, it cracks as it dries and takes a whole lot longer to dry (26 hourd plus and it's still wet in spots

so what do you guys prefer?

btw I thought I was the only one into trains in Texarkana
 
How are u applying it? layers? or one big gob of it at a time? and u are applying on styrofaom?
 
I vote for plaster of paris for the most part and hydrocal if I have to carve rock hydrocal is so expensive
 
I used drywall mud to make tater mountain. I applied it in one coat about 1/8 inch thick, let dry 24 hours and sanded it smooth. If you got cracks you applied too much or tried to fill too big a crack. It's okay, just use a second coat. Plaster of paris dries in 10-15 minutes and is too hard (as in not soft) to work with for landscape. Drywall mud is easier to work with when dry.

mountain03.gif


traincity38.gif
 
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Alcomotive said:
How are u applying it? layers? or one big gob of it at a time? and u are applying on styrofaom?
Click to expand...


He was making a good point here, We noticed when we applied anything over styrofoam it tended to crack because the styrofoam seems to dry it out too fast. even when we tried newspaper/paper towels in plaster; same results..(now this is builder board type styro with paper like backing not stacked insulation, packing like stuff I am speaking of)
 
For the best, detailed , results I use plaster of paris. Yes it is going to be hard but when I have to carve for example rocks I do that starting about an hour later.( It is very soft and easy to carve/cut) If I cannot finish it in one day I make it a little bit wet the next day and the surface is again easy to model with a pin or sharp knife....
And yes you have to wait 24-48 hours( heated room) before adding/painting a primer on it. In the meantime you can watch and proof/compare your "piece of art" if it has became the way you want it. If not: ACTION!!:eek:
BTW : the cracks are may be also the results of to much water you added to the joint compound or plaster of paris,and always add the "powder"to the water and not the water to the plaster of paris powder....
Last but not least: use "fresh" stuff! When it is getting older the moisture in the air will start very slowly a reaction that should actualy start on your layout and not for a year or so in the shop on the shelves:rolleyes:

Jos
 
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WOW Jos! Beautiful details on that stone work..And too much water, older bag or the mixing order might have been our problem...(or a combination of all 3)
 
Plaster of Paris is good to use it's just that you have to make small amounts at a time and work it fast ! It dries very quickly. I buy a big tub at WalMart very inexpensive there .
 
Tater Mountain? It looks more like Cowpie Mtn in the pic.... :D

I use Sculptamold, generally. But, I haven't done a large hill or whatever yet.

Kennedy
 
wow on the tater and the castle guys!!!

Grove den I am using the redi mix kind, all you do is pop the lid open give it a quick stir and start sculpting (in small measurements as I have now learned!)


....boy why didn't i find you guys before Christmas!!! well,...at least my daughter is getting to watch her train run around the track w/out any electrical problems!!!
 
Plaster of Paris is by far the best I have used for large projects. It's cheap, strong, and other than cleaning up...easy to use. I cover mountains, use in rock molds, globs for carving rocks and etc, and as filler. Setting time can be delayed by adding a jigger of vinegar to the mix.

I like a "covering" mixture with the consistancy of pancake batter and use about 3 cups per batch. For carving rocks and things, I make almost a paste. If you want a rough texture, add some Vermiculite. This requires a little more water to your batch, as it will absorb water itself.

Anyone in the drywall business will tell you that mud will crack if applied too thick, including readi-mix. Even if you layer, you have to be careful and must wet the first layer or it will take the moisture out of the new one causing it to crack. A good use for readi-mix drywall mud is making automobile roads applied about 1/8"-3/16" thick.:)
 
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I have been working on my layout for 2 yrs now and have been using drywall mud mixed to different thicknesses as needed. I have a 24'x24' layout with mountains from a 30" bench height up to 6". I used chicken wire for the forming and stitched on a layer of recycled window screen on top. Using diluted mud I soaked newspaper and/or screen and built up in layers. Let each layer dry and between layers take a 6" brush and put on about 3/16" of mud. I then added rocks that I cast using Woodland Scenic rock molds that I cast with the 45 min fast patch drywall repair powder that you have to mix. All these items are a by product of my business but are also very inexpensive. Play with the mud to get a consistency you like for diff things. It can be wire brushed or scraped for diff effects and can be done wet or dry.

Someone mentioned getting it and other things to stick to foam and the like. I have had success in painting the foam/styrene with a coat of contact cement and letting it dry then mud over it. Works great.

Good luck in your endeavors
 
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