One Third Under Plaster

Model Railroader General Discussion (Model Railroader)
1

I woke up yesterday thinking about plaster, moved the building markers and trees out of the way, and when the day was over, more than a third of the layout is sporting a new coat of plaster cloth. Just before turning in, I also went crazy with a butter knife and lightweight spackling compound and carved some detail into a rock face.

No pics yet, but a question did raise its ugly head. The plan was to lay the first layer of plaster cloth to get the general shape of the streambed in place, then lay down sheets of plastic kitchen wrap with duct taped joints, and then a second layer of plaster cloth over the top, to make a liquid tight bathtub for the creek, in order to keep water modelling compounds from leaking through the table onto the carpet underneath.

The ugly thought that popped up while laying plaster cloth was "What if water modeling compounds EAT Saran Wrap?

So…do they? I’ve been looking at the standard methods, acrylic medium and maybe WS water beads for a waterfall. I’m going to put down a dropcloth, but if the streambed fails spectacularly, then enough plastic water may leak to get onto the carpet anyway.

How well do these chemicals get along together?

2

I used one layer of plaster on top of plaster cloth to make my fishing pond and when I did the first pour, there were no leaks. And that was without any plastic wrap.

3

Over concrete, i’d be willing to take a chance, but this is my dinng room and I want to be sure things don’t go wrong.

It’s good news that a layer of plaster held your pond material while it set up, that means plaster alone may keep the chemicals from getting the chance to interact. All told this cavity for the river is about 5 feet long, too many opportunities for problems to pop up due to the method of construction, mani table support members, all kinds of stuff going on under here.

Thanks for the response.

4

Remember, you are going to paint the plaster cloth, and that will provide a leak-proof seal.

So do the first layer of plaster cloth to get the shape. Do a second as well. Supposedly, that alone is sufficient to make things watertight. If you are concerned, you could mix a small amount of plaster and pour it in to give a smooth, continuous streambed. (Please don’t have an angled bed, though, as it can cause headaches; you are better off with level steps that can be masked with rocks and such.) Again, you paint that, and you are fine.

You might want to construct a wooden dam at the edge of your layout to prevent anything from flowing onto the floor. Still put several layers of newspaper there to catch anything.

Also, when you pour your water stuff (like Woodland Scenics Realistic Water), do it in small, thin pours. Let it cure for a little more than 24 hours.

I’m kind of in the middle of this stuff myself…read about it on page 2 of the link to the thread, below.

5

Sounds like a lot of plaster! That can get a bit heavy. Although I use plaster too , I try to use it as a thin layer over pink or blue insulating foam, as it keeps it lighter.

6

All I used for my river and lake was a thin layer of powdered wood sandable putty mix, and I also painted the river “bottom” with acrylic paints. The only places I had to be careful were on the banks if foam sheeting met and left sizeable gaps down to the river bottom, and at the end of my table. At the ends, I used masking tape pressed throroughly onto the edge, and for the possible leakage points along the banks, I made the wood putty rise up to cover them.

Short answer, if you seal the bed and banks with a layer of putty or plaster, they will become impervious to the epoxy or other material meant to depict water. Painting only improves it.

7

One good way to test for leaks is to shine a bright light under the plaster. Any place you see light coming through probably needs a patch to strengthen and seal it. I would also suggest a test pour with water before you commit to the water compound. They will tell you if you have any leaks and water leaking through should be easier to deal with than the compound.

8

If you decide to use Saran wrap you can cover the wrap with a thin coating of plaster, then paint the river or pond bed with an appropriate color to give you that water color you want.
Instead of using Envirotex one system that works really well and you can replenish every so often to shine it up a bit is gloss acrylic medium, sold at hobby stores, i.e. LHS, Hobby Lobby, Craft Stores, Wal-Mart.
The acrylic gloss medium won’t disolve the plastic wrap, is water soluble, and easy clean up. Most of all no smell or ffumes. It is white when you first put it on, but thenit dries clear.
Every so often when you want to shine it up a little bit put another layer on. If you allow it to get tacky, say a 1/2 hour or so, go back and use a brush and with stippling technique you can raise the gel and make waves.
Please remember there is acrylic gloss medium which will give a clear shiny appearance, and acrylic matte medium which is used for lots of things and projects, one of course is applying it to ground foam and ballast to glue it in place.
WTRR
Yard Office

9

Thanks for all the replies, good info there.

The plaster cloth I’m using is see through after installation, sort of a gauze appearance. The holes are small, about like a window screen after being painted, and I’m not sure even two layers will form a seal. Two layers plus paint will be an improvement. The benchwork was not designed as a bowl, far from it. Basically the stream bed is 2x2, scabbed on the 4 inch main frame, covered top only with luan, and then many small pieces of foam forming the banks. Lots of potential for leaks.

The plan was to use about three pours of Envirotex, one surface layer of Acrylic gloss for waves, all stairstepped in rockdam pools, with the WS beaqds used for the spillways and falls. The waterfall WS uses in advertising looks good, but I’d still like to hear from people who have built nice waterfalls at home before committing to that approach.

I’m enjoying this phase of construction. The plaster cloth is a joy to use, cleanup takes about 2 minutes, and the pre-mixed lightweight spackling compound is awesome too. Pop open the tub, ladle a styrofoam cup full out, butter knife to sculpt, you can pop in, accomplish a lot and be back out and cleaned up in half an hour.

The spackle has the consistency of shaving cream, it could stand to stick to plaster cloth a little better, but I’m going to try moistening the plaster cloth to see if that helps. Once it’s smeared on, it sticks good, but getting it stuck first takes some fingerwork.

Not too concerned with weight at this point. The plaster cloth and lw spackle is like building with air compared with benchwork, plywood, even styrofoam.

10

I don’t see how Envirotex would eat through plaster or suran wrap, but you can always put down drop cloths untill everything dries. I don’t see how you would have any problems after everything cures.[2c]

11

Might want to support the botton with a carboard strip foundation, and wide set duct tape can work wanders on smoothing the look out… if it isn’t old and sticks well. Good luck!

12

In you remarks I think you said the plaster cloth leaves little spaces like the holes in screen wire ever after two coats? Sound like you are not smoothing our the wet plaster on the cloth after you drape it over the forms. When I use WS plaster cloth, I use my fingers to kind’a smooth out the wet plaster so there are no holes. Then when the next layer of wet plaster cloth goes on and the same process is used, there will be NO holes at all. After that a coat of base acrylic paint some bottom “clutter” sand and rock banks and POUR the water. I don’t think you will have any leaks.

13

Have you considered using “Magic Water”? Absolutrly foolproof. Its on ebay and at www.unrealdetails.com

14

I just used scalptimold instead of plaster on my lakes and rivers. Then I painted the scalptimold before adding Woodland scenics Easywater. Did not leak and made a real nice scene. santaferailroad

15

I use 2 layers of plastercloth whenever I am covering something up. Put the first layer down, wetting the edges to adhere it. After 10 minutes or so, add a second layer. Then, using a cheap brush, liberally wet the entire surface, continually brushing. The plaster will float to the surface from both layers, and will seal all the holes.

16

Thanks for all the replies, good information here. I’m currently (test) painting the plaster that is laid so far, and I hope to have some pictures up over the weekend.