gluing and painting plaster of paris parts for a diorama

Glue with PVA glue (Elmer's School Glue or equivalent).  You may want to use some toothpicks or small wooden dowels at the seams to strengthen them as well.  If you are using acrylic paints, there should be no need to prime.  Just paint away.

I cast scenery rocks using plaster of paris for my HO scale model railroad. I will tell you a really handy tip that produces some great results in the absolute easiest way.

Make a wash of "wet water" with black India Ink. You can find recipes for this everywhere but the general idea is a typical Windex sized empty spray bottle, 1 cap full of Dawn dishwashing liquid (or similar), and 1 teaspoon of India Ink. Adjust the ink up/down to your preference. That ink is potent stuff! A little goes a LONG way!

Spray your cobble stone street while laid flat, and the ink will settle into the mortar crevices making those areas darker. You'll get a really beautifully toned gray result because of the way the plaster readily absorbs the wash. You can spray more to get a darker effect.

Be careful not to get carried away and go too far. Your initial results will look awesome but you might want it a bit darker. Watch out because the tone can change a bit when it dries! At first the plaster is so dry it absorbs the wash and dries out almost instantly. But once the plaster gets saturated and damp, it will look darker than it really is (think of your concrete driveway after its rained and how it turns light gray in the areas as it dries up in the sun). Really damp saturated plaster castings can take 24 hours to dry all the way back to their true color.

You can't remove the ink from the plaster once it's in, so I repeat - don't spray too many coats of wash or you'll regret it.

You can also do a similar wash with cheap acrylic paints like those sold at Walmart for 50 cents per 2oz bottle.

I leave you with this tip because I've spent many hours doing MUCH more laborious multicolored painting to my rocks to get the desired tones/shadings/effect, and sometimes I shake my head and wonder if it was all worth it when the results I got in 30 seconds using this ink wash method were almost as good.

There's something about the way the plaster absorbs the ink that gives awesome relief and highlights. (The opposite result of spraying a gray paint on the plaster which would give you 1 solid color with no shading whatsoever.)

I like epoxy.  5 minute epoxy sets fast and scuplt all used at the seams can be sculpted to match whatever the need is. I like to use a acrylic sealer in a spray can as plaster is absorbent to a degree leaving a "dead flat" look most outdoor paint is a semi gloss that gets a flat look when dirty. Really its a matter of tast.

Hi Gino !

Thanks a lot !

I'll give it a try.

I have never had an issue painting it with acrylics without a primer. I have used CA glue in the past and that works, by Gino's suggestion might be a better option.

Thanks Bish,

I think i'll give both glueing suggestions a try depending on parts size.

Thanks for Your tipps  and for the time You took to answer in such Detail !

Thanks a lot Payitforward. With alll the answers I got so far i thinmk I can start my Project now.

I use Titebond Wood glue for plaster. I like it because it isn't as messy as epoxy and it's thinner in the joints. A trick that I found is using a few dabs of hot glue as a clamp until the wood glue dries. The hot glue doesn't stick real good and it's easy to pop off a few hours later.

Hi daveinthehat,

Thanks for taking the time to reply to my question!

I always seal plaster before painting. Plaster is a very absorbent material and will suck up loads of paint. Seal it with primer, then paint. Your results will be much better! :)

Hi scalebricks,

thanks for responding. I never expected to get so much good advice via this Forum !

Happy to help!

Hi,

a (rather long) time ago i asked about how to work with plaster diorama components.

My job and other influencing factors have forced me to pause my project.

Now I am happy to say that I managed to complete the planned diorama.

Thanks again to all that helped me get started.

I am including a few pictures for You to see.

Any comments or suggestions are welcome !

Helmut

http://s1160.photobucket.com/user/Helmut_Rohrer/media/dio_SVPM/EOS%20100D2017_03_050027_zpsiiw4chg4.jpg.html

MrConductor

I cast scenery rocks using plaster of paris for my HO scale model railroad. I will tell you a really handy tip that produces some great results in the absolute easiest way.

Make a wash of "wet water" with black India Ink. You can find recipes for this everywhere but the general idea is a typical Windex sized empty spray bottle, 1 cap full of Dawn dishwashing liquid (or similar), and 1 teaspoon of India Ink. Adjust the ink up/down to your preference. That ink is potent stuff! A little goes a LONG way!

Spray your cobble stone street while laid flat, and the ink will settle into the mortar crevices making those areas darker. You'll get a really beautifully toned gray result because of the way the plaster readily absorbs the wash. You can spray more to get a darker effect.

Be careful not to get carried away and go too far. Your initial results will look awesome but you might want it a bit darker. Watch out because the tone can change a bit when it dries! At first the plaster is so dry it absorbs the wash and dries out almost instantly. But once the plaster gets saturated and damp, it will look darker than it really is (think of your concrete driveway after its rained and how it turns light gray in the areas as it dries up in the sun). Really damp saturated plaster castings can take 24 hours to dry all the way back to their true color.

You can't remove the ink from the plaster once it's in, so I repeat - don't spray too many coats of wash or you'll regret it.

You can also do a similar wash with cheap acrylic paints like those sold at Walmart for 50 cents per 2oz bottle.

I leave you with this tip because I've spent many hours doing MUCH more laborious multicolored painting to my rocks to get the desired tones/shadings/effect, and sometimes I shake my head and wonder if it was all worth it when the results I got in 30 seconds using this ink wash method were almost as good.

There's something about the way the plaster absorbs the ink that gives awesome relief and highlights. (The opposite result of spraying a gray paint on the plaster which would give you 1 solid color with no shading whatsoever.)