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I have always sculpted my rocks from foam, but lately I've been seeing people using rock molds from Woodland Scenics and casting them out of hydrocal. I'm working on my Armies on Parade board, and I think this would be better with molds as I don't have a ton of room to work with. My big question is how do rocks made this way hold up? When I first started making terrain eons ago, I used plaster and that made stuff heavy and it would crack and get all over the place. Not sure if I was just such a noob back then I wasn't doing it right or what. The board is already pretty heavy (I'm using 1/4" MDF) and I'd rather keep it light if possible. The terrain bits will be removable so I want to make sure they can stand up to transportation and gaming. Thoughts?

My experience with this product is that it has always been a little fragile to chipping, but I believe that comes down to the accuracy in measurements of the mix and water.

Too much water and it becomes too brittle. More of the mix and it is likely to be firmer.

I think they're probably designed more for static model railway type applications rather than wargaming where they may be bashed or have models placed on them which could chip.

Personally, I'd do it from foam.

 Oppl wrote:
My experience with this product is that it has always been a little fragile to chipping, but I believe that comes down to the accuracy in measurements of the mix and water.

Too much water and it becomes too brittle. More of the mix and it is likely to be firmer.

I think they're probably designed more for static model railway type applications rather than wargaming where they may be bashed or have models placed on them which could chip.

Personally, I'd do it from foam.

Thanks for the reply. Yeah, that's what I was thinking and the way I was leaning. I might try those molds with resin and see how that works.

I haven't used those moulded rocks myself, but a thought anyway; you could finish them off with a decent layer of something to protect them, some people use PVA or latex paint.

I have used foam coat and modge podge for sealing foam before. Works well. I just don't think it'll make these rocks strong enough. Watching people cast them on YouTube and demolding them you see a lot of cracks and broken pieces. Good thought though.

it takes practice but honestly they don't seem too fragile. I wouldn't want to drop them and step on them of course, but for normal use - sure. I have buildings made from blocks made from molds from Hirst Arts (who I highly recommend if you want to start doing this sort of thing). There's also really good instructions on molding on the Hirst site. Some of the best youtube videos on this subject are from LukeTowan, The Terrain Tutor and Terranscapes imo

For rocks, I've actually found a mix of foam and molded rocks work very nicely. I like to use the foam as a base, for the hill part, and rock molds to make some of the faces. This started out as a necessity as I had used the Woodland scenics mold, which I found a bit difficult to demold (also likely because I was still learning and made the mix too brittle).

Anyway, if you're planning on taking your terrain to the FLGS for use, I would probably steer away from using molded stuff. It can get pretty heavy for one thing. If you're not going to be transporting it, but just using it at home, then go for it.

You can add the pva to the mix of plaster and water - it adds some resiliency to the casts.
You can also tint the plaster with oxide powders (like for concreting) so you don't get the white chipped areas - which you will get because it WILL chip over time.

Hmm never heard of PVA + plaster.

anyway. most people use hydrocal which is pretty durable stuff.

though you can cheap out by bugging your family dentist for dental plaster which is some TOUGH stuff. though its usually pink.

If its going to be a one off armies on parade board then i wouldn't think it would need to be that tough. you could probably just do regular plaster mixed in with poly fill to keep it fairly light OR do a slush cast first of pure plaster then after the shell sets put in a lighter support material.

Oh, I didn't mean JUST PVA and plaster. Mix about a tablespoon of goo into the 1/2 litre of water (essentially, mix the plaster into a glue slurry rather than just water. It also plays with the surface tension).

PVA retains flexibility even when cured and it will impart this to the plaster - it just makes it a little more resistant to chipping.
It won't do diddly-squat if the pieces are dropped onto the floor, but a small impact s less likely to damage the surface.

That said, ALL my plaster terrain was varnished with a urethane sealer, and that stuff will resist all but xylene (which is rather hard to get here).

 chromedog wrote:
Oh, I didn't mean JUST PVA and plaster. Mix about a tablespoon of goo into the 1/2 litre of water (essentially, mix the plaster into a glue slurry rather than just water. It also plays with the surface tension).

PVA retains flexibility even when cured and it will impart this to the plaster - it just makes it a little more resistant to chipping.
It won't do diddly-squat if the pieces are dropped onto the floor, but a small impact s less likely to damage the surface.

That said, ALL my plaster terrain was varnished with a urethane sealer, and that stuff will resist all but xylene (which is rather hard to get here).

Neat

cool to know.

made a couple of small scatter out of dental plaster and even dropped onto hardwood has yet to break. but still it doesnt sound like he needs anything too crazy. i feel like normal plaster will be fine so long as he isnt throwing this display board around like nuts.

I wonder if you did chromedog's PVA trick then also threw some chopped strand fibreglass (which is quite cheap) in if it'd make it reasonably tough. Depends on the elasticity ratios and how well it bonds to the glass I guess.

Is this for cliff faces or just rocks in general?

If it's cliff faces and for an Armies on Parade board I would use cork bark rather than plaster as it's much lighter.

I would think plaster would be a bit heavy.

For some context, here is what I'm doing.



This is for my Armies on Parade board for my Blood Angels, but I want the Fortress of Redemption removable so I can use it as a piece of terrain when I get around to making my own table. I saw someone else do something similar with the fortress and thought it looked great.

 Guildenstern wrote:
it takes practice but honestly they don't seem too fragile. I wouldn't want to drop them and step on them of course, but for normal use - sure. I have buildings made from blocks made from molds from Hirst Arts (who I highly recommend if you want to start doing this sort of thing). There's also really good instructions on molding on the Hirst site. Some of the best youtube videos on this subject are from LukeTowan, The Terrain Tutor and Terranscapes imo

I didn't realize Terrain Tutor used the Woodland Scenics molds. That was super helpful. I've used Hirst Arts stuff before. The results are good, but really all that casting isn't for me. I'd rather sculpt it, kit bash, or scratch build. Looks better IMHO. How these rocks are on this board makes it a pain to sculpt though and I'm not against some casting. I think too much Hirst Arts pieces and things start to look predictable. I don't know. I'm just weird I guess.

StraightSilver wrote:If it's cliff faces and for an Armies on Parade board I would use cork bark rather than plaster as it's much lighter.

It is for cliff faces and I was thinking about giving that a go. Where can you buy it? I don't want to wait for it to be shipped.

AllSeeingSkink wrote:I wonder if you did chromedog's PVA trick then also threw some chopped strand fibreglass (which is quite cheap) in if it'd make it reasonably tough. Depends on the elasticity ratios and how well it bonds to the glass I guess.

Yeah, I might have been overthinking this. Really where the rocks will be on this board won't see a lot of play. I'm going to try the rock molds with hydrocal and the PVA trick (or dental plaster if I can find it locally). I'll also try and find something to tint the hydrocal with as I don't want it white for when it chips. Going to look into cork bark too. Not sure if I can get it locally, but apparently some pet stores have it. Thanks all!

I think cork bark would be perfect for that tbh.

I usually buy my cork bark from a model railway supplier or specialist model shop but I'm based in UK so not sure how far you're nearest one would be in US.

Otherwise you can buy it in pet stores - usually in the reptile bit. It comes in pretty big pieces if you buy it from pet stores but you can break it up into more manageable chunks.

Once you've broken it up you can stick it on and then use polyfilla and sand to hide the gaps / joins.