How to color plaster cast rocks

[Bob]

So, I have made the first part of a rock but on the CSX Cumberland Division and will post photos soon.  I am not happy with the color.  I pretty much followed what woodland scenics suggests.  After the plaster dries, is add three diluted colors from their earth tones collection, and while they look ok they just are not dark enough.  I've tried adding more color layers, but this is not darkening the rock much further - I'm guessing the plaster has absorbed all of the color it can?  Any advice on this?  Should I use more concentrated colors?  Maybe add some concentrated gray paint to the plaster while mixing it?  I'll get something up on the layout thread in a day or two.  Bob

[Dave V]

Heh, I spray my rocks with rattle cans and then drybrush them with various earth-colored acrylics.

[Bob]

Thanks Dave - I"ve cast some more rocks and I think I will try that.  Bob

[CRR Chase]

So, I have made the first part of a rock but on the CSX Cumberland Division and will post photos soon.  I am not happy with the color.  I pretty much followed what woodland scenics suggests.  After the plaster dries, is add three diluted colors from their earth tones collection, and while they look ok they just are not dark enough.  I've tried adding more color layers, but this is not darkening the rock much further - I'm guessing the plaster has absorbed all of the color it can?  Any advice on this?  Should I use more concentrated colors?  Maybe add some concentrated gray paint to the plaster while mixing it?  I'll get something up on the layout thread in a day or two.  Bob

I paint with acrylic paint from the arts and crafts section, then after that dries I use a dry brush and weathering powder technique to bring about the desired effect.. The base coat always leaves alot to be desired. its the dry brushing and powders that bring it out and make it pop. powders for shadows, dry brush for highlights. 

[signalmaintainer]

I brush a dilute India ink solution over the white plaster or, in my case, Sculptamold rocks. Then, like Dave, I dry brush acrylic burnt umber, raw umber, burnt sienna, yellow oxide and black (go easy) as needed to build up depth. Then I follow up with India ink washes as needed.

The black strip in this rock formation is a coal seam.



I stopped using acrylic stains decades ago, as I found they did not give the same depth and results as oil stains.

[Bob]

Interesting - I think I am going to tear out what I have done and try again.  I should have posted this question before I tried the stains!  Hopefully some others will weigh-in.  Seems like there are a number of approaches.  The coal seam is a very nice touch by the way!

[Scottl]

I've tried both staining and painting the casts.  The latter is advocated by Mike Danemann in his articles and books which is why I tried it with my first efforts.

I find that staining works best when the cast is not completely cured.  I work with Plaster of Paris and it is still damp for hours after it sets.  At that point, the stains seem to penetrate better and I get better results.  Darker rock like coal is probably best accomplished with painting, but most other rocks have a lot of very light highlights that I think are better captured by staining.  The concentration of the stain is a factor in how well it covers as well.  I use diluted acrylic paints.

My experience with painting the entire rock is that you get an uniformity in color that is very unnatural, even with aggressive top coating and dry brushing.

I have experimented in the past with tinting the plaster during initial mixing with water.  This does give some useful initial color but slows the cure of Plaster of Paris considerably, and I think would be hard to replicate between batches.  Both of these might be considered features if you want to do some additional carving or staining while damp.

[wazzou]

These are some of the older Woodland Scenics molds cast in plaster.
I just sprayed them with a Rattle Can Primer prior to installing and then used some Craft Acrylic paints.
I highlighted them with a really light gray "dry" brush and then finally gave all of the nooks and crannies a heavy dose of India Ink and IPA to highlight the shadows.

[John]

I follow this guy ... spend 15 minutes on this video for some ideas - the glazing is the secret

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[CRR Chase]

These are some of the older Woodland Scenics molds cast in plaster.
I just sprayed them with a Rattle Can Primer prior to installing and then used some Craft Acrylic paints.
I highlighted them with a really light gray "dry" brush and then finally gave all of the nooks and crannies a heavy dose of India Ink and IPA to highlight the shadows.

What he did with the india ink at the end is what i do with powder, to each their own, there is no "right" way.. but plenty of wrong ones lol.

[Chris333]

I spray rockwork with Rustoleum camo khaki and then add washes.

[Angus Shops]

And I thought I was the only person who uses rattle can primer on my rocks! I like it because it ‘glues’ all the little bits of plaster that get stuck in the crevices (if you’re a ‘carver’ and you don’t vacuum to hard) to get that loose debris look I like. Then overspray as required - I use, among others, Woodland Scenics ‘concrete’, thinned, in my airbrush for the basic Rocky Mountain shale colour.

[basementcalling]

Whatever method you settle on, consider adding a tint to the plaster you do use. All casting eventually chip on our layouts, and tinting the plaster you use can help hide or blend the resulting area. Few things scream out worse than a bare white chipped spot on a rock face. And touch up is always hard to do well.

[wm3798]

Whatever method you settle on, consider adding a tint to the plaster you do use. All casting eventually chip on our layouts, and tinting the plaster you use can help hide or blend the resulting area. Few things scream out worse than a bare white chipped spot on a rock face. And touch up is always hard to do well.

This^^^
I blend some craft acrylic into the plaster mix from the start.  The long term benefit is the elimination of white chips later.  The short term benefit is that a lazy, easily distracted person, such as myself, can have "rocks" with a minimum of effort, which in time, could get weathered...



Turn them out of the mold, glue them down, throw around some ground foam and bip bop bip!

Lee

[nkalanaga]

When I was doing my rockwork, 20+ years ago, I also used craft acrylics.  In my case, I mixed them into a 2-liter bottle of water, then made the plaster with that.  No problem with chips, or lengthening the setting time.

And, as Scottl says, if you're staining it, do it while the plaster is still damp.  It seems to work a lot better.