Plaster use

[jkinosh]

I am not sure where this should go, or really a subject for it, but here it goes.

I am wondering if it is possible to this down Joint Compound and use it to mold some ojects or use it with papertowels as overlay on foam to make some mountains. I just finished remodeling our bathroom, and have half of a 5 gallon bucket left, and would like to be able to put it to use.

Thanks for your help,

Jacob

 

[MasonJar]

Jacob,

Joint compound is a very common landscaping material. Since you have a 1/2 bucket kicking around, try a few experiments and see how it goes. As for using it in moulds, I am not sure that it would be able to pick out the details of "finer" objects, but it is worth a try. Let us know how it goes (preferrably with pictures... )

I would have used my leftover joint compound, but I left it in the garage and it froze...

Andrew

 

[jkinosh]

I think I may try it tonight, The molds I was thinking of are not extremely detailed, I was thinking of using it to make some retaining wall for a river with a bridge, But I will post some pictures and let you know when I get it finished.


Jacob

 

[ezdays]

I have used joint compound to free-scape rocks. I bought some rock molds a few years ago and never used them. What's good about joint compound is that unlike plaster, it takes a while to set up. I've gone back and reworked rock outcroppings a half a day later and it was firm, but workable.

The point is, if you used joint compound with molds, wait at least 12 hours for it to set up before you take to mold off.

 

[jkinosh]

Thanks for the tip, I'll let everyone know how it come out.

Jacob

 

[doctorwayne]

I'm not too fond of this stuff for model railroading. I used some to make roads, and while it is easy to work, it's also very soft and is easily damaged. Also, if you don't seal it, it can be resoftened when building water-based scenery. (you know the kind where you spread the ground foam, ballast, whatever, then spray with "wet" water and apply diluted white glue.) I had to bring in the road repair guys after the scenery crew left. I can't imagine that it would be much good for either scenery or castings due to its softness and lack of strength. But, since you've got some left, and it seems that others have had better luck with it than I have, you might as well give it a try.
Wayne

 

[ezdays]

Wayne,

Not to dispute what you said, I can only go by my own experiences and I've not had problems with painting joint compound, or with gluing on scenery, and never had it soften up. Maybe it's the type of compound I've been using, but once it's hard, it stays hard. I like it because it can be worked for so long before setting up. I've gotten some neat effects using joint compound. The trick is to wait a few hours before you start shaping it. I've applied it in the afternoon, shaped it in the evening and the next morning I was still able to do some some final touchup.

Now, on the only road I've built so far, I've used plaster and I'll probably use plaster for roads again because it drys quickly and can be trowled really smooth as you go.

 

[doctorwayne]

Don, I think the reason that my roads resoftened was that they weren't painted. I made a really thin wash using Polly Scale paint, then used this to stain the joint compound. It took a couple of applications, and I had to be careful not to "work" the brush too much, as the compound softened with the first coat. It looks pretty good though, and if I mar the surface, I just mix up a bit more stain and paint it on like a patch. The only reason I used it in the first place was because it's easier to sand than the patching plaster that I use for scenery, and bridge piers and abutments.
Wayne

 

[ezdays]

Wayne,

One thing I have found is that it is difficult to get joint compound really smooth. A fact that isn't a problem when doing rocks or even flat land. An asphalt road in N scale however, has got to be glass-like smooth or it won't look realistic, as far as I'm concerned that is. I can achieve that with plaster of paris. I guess I could sand the joint compound, but I tend to be lazy when it comes to doing that.

 

[jkinosh]

Well, Here are the results so far. On Monday Night I made a Retaining wall form, Approximately, 1.5" x 4 " x .25", and as of this morning it is still soft to the touch, and does not seem to be setting up completely, I have it sitting on my workbench directly under a heat vent, so I know it is warm enough. I think I may try the Joint compount for rock surfaces on a mountain, but will probably avoid it for making molded parts.


Jacob

 

[ezdays]

Well, Here are the results so far. On Monday Night I made a Retaining wall form, Approximately, 1.5" x 4 " x .25", and as of this morning it is still soft to the touch, and does not seem to be setting up completely, I have it sitting on my workbench directly under a heat vent, so I know it is warm enough. I think I may try the Joint compount for rock surfaces on a mountain, but will probably avoid it for making molded parts.


Jacob

I agree with you, the molds trap the moisture and it can't evaporate. Unlike plaster that drys by chemical reaction, joint compound hardens by air drying and heat won't help if there's no place for the moisture to go. If you had one side of the mold exposed, that should do the trick though.

 

[doctorwayne]

Don, that brings up another problem that I'd forgotten about regarding drywall compound: it seems to have a tendency to crack as it dries if the application is too thick, as it most likely would be in a casting. The stuff that I used for my road has a suggestion on the container that, when doing drywall, the compound, after it has hardened, can be smoothed with the use of a damp sponge if you want to avoid the problem of sanding dust.

Wayne