When I go to the USG site for Hydrocal I find 9 different casting products. Can anyone say specifically which one I should use for casting a rock face?
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Greg, any plaster (even stuff from the hardware store) will work for this application but I would try the three on the bottom row: casting, # 1 casting or art. Regular Hydrocal is often used but more expensive than the others. I'm not sure there's anything to be gained by using it.
Greg,
As Dennis said, any plaster will do nicely. I used to use Hydrocal for rocks and tunnel portals many years ago (HO era for me) but switched to plaster about 25 years ago and don’t regret it. I usually buy mine at Home Depot, I believe 25-lb bags. You may try slightly different ratios (water to plaster) and see which you like best.
I also have switched to StructoLite for ground and hillside cover, and it works well – it has a more realistic texture and a long working time. However, I tried it for castings and it just didn’t work well for that.
Good luck!
Alex
As Dennis said, any plaster will do nicely. I used to use Hydrocal for rocks and tunnel portals many years ago (HO era for me) but switched to plaster about 25 years ago and don’t regret it. I usually buy mine at Home Depot, I believe 25-lb bags. You may try slightly different ratios (water to plaster) and see which you like best.
I also have switched to StructoLite for ground and hillside cover, and it works well – it has a more realistic texture and a long working time. However, I tried it for castings and it just didn’t work well for that.
Good luck!
Alex
Greg,
I used hydrocal for actual castings, I did a web search and found a local place to buy it, it was inexpensive, like $20 for a 50lb bag or something like that, will last me for some time,
Like Alex, I use strucolite for building mountains, easy to work with, and I like the texture
I used hydrocal for actual castings, I did a web search and found a local place to buy it, it was inexpensive, like $20 for a 50lb bag or something like that, will last me for some time,
Like Alex, I use strucolite for building mountains, easy to work with, and I like the texture
quote:Originally posted by gregj410:
When I go to the USG site for Hydrocal I find 9 different casting products. Can anyone say specifically which one I should use for casting a rock face?
When I bought a bag 10 years ago, I bought the same stuff thatwas recommended when I bought my first bag 20 years ago, grade B-11. That was what was recommended 20 years ago by the dealer for "model railroad scenery". They didn't have 9 different grades then, but had about five.
I didn't see the B-11 name, so I typed "hydrocal model railroad" into the USG product locator, and this link came back:
Hydrocal White
Hope this helps.
Regards,
Jerry
Hi Greg,
I've used several variations of casting plaster for different projects. Dennis and Greg are correct that most plasters will work, but there are differences that need to be taken into account.
The "plaster of paris" that you'll find at the hardware stores has varying percentages of filler (usually fine ground silica). The filler is cheaper than the gypsum, which is why the stuff at the hardware stores costs less. The down side is a loss of strength. For rock castings that's usually not a big deal once it's installed. However, there is also a loss of "green" strength. This is the strength of the plaster when is hard, but not yet fully cured. Generally, "green" castings feel slightly damp while fully cured castings feel totally dry. As long as you get the rocks out of the mold intact you're fine. If you have problems with cracking the rocks you'll need to let it sit in the mold longer to cure before removal. The other downside is that the filler doesn't sneak into all the tiny nooks and crannies in some fine castings. The surface finish is a little fine. Again, for rock castings this usually isn't a big deal.
The "HYDROCAL® White Gypsum Cement" is the product I use most often for rock castings. It's much stronger in the "green" state than the hardware store plasters. That lets me make a copy out of each mold in less than an hour. It also has a finer surface finish that picks up the little details in a good rock mold. If you're using Woodland Senics rock molds this is over kill. The WS molds aren't that finely detailed. I mostly use molds from Bragdon Enterprises, which have a lot of fine detail and deep reliefs. Hydrocal White is noticeably better for this quality of a mold. When in doubt, this is the best plaster to try on a new project. It's also pretty inexpensive if you can find a local supplier that carries it in 50 or 100 lb bags. Your best bet will be a concrete supply house in an area with lots of historic homes. It's often used for plaster crown and ceiling moldings.
The "HYDRO-STONE® Gypsum Cement" is the best of the best when it comes to model railroad casting plasters. It has the highest surface finish with good "green" strength. I use Hyro-Stone when casting tunnel portals or other man made objects where small imperfections in the surface are most noticeable.
The other plasters from US Gypsum are tailored for other application. Drystone is a quick set product often used for rapid prototyping and not really suitable for rock making. Hydrocal Statuary is very similar to Hydrocal White, but is modified to work better in hollow molds. It works fine for rock molds. Tuf-Cal and Tuf-Stone are fiber reinforces plasters. These don't work very well for rock castings. When you apply color washes to the rock surface the fibers tend to leave a fuzz on the surface. The other three on the USG site (USG #1, USG Molding/Casting, and White Art Casting) all have a surface agent that helps paint spread on the surface rather than quickly absorbing into the plaster. This is great for molding things you want to paint, but it makes it more difficult to apply color washes on rocks that need to soak in.
I've used several variations of casting plaster for different projects. Dennis and Greg are correct that most plasters will work, but there are differences that need to be taken into account.
The "plaster of paris" that you'll find at the hardware stores has varying percentages of filler (usually fine ground silica). The filler is cheaper than the gypsum, which is why the stuff at the hardware stores costs less. The down side is a loss of strength. For rock castings that's usually not a big deal once it's installed. However, there is also a loss of "green" strength. This is the strength of the plaster when is hard, but not yet fully cured. Generally, "green" castings feel slightly damp while fully cured castings feel totally dry. As long as you get the rocks out of the mold intact you're fine. If you have problems with cracking the rocks you'll need to let it sit in the mold longer to cure before removal. The other downside is that the filler doesn't sneak into all the tiny nooks and crannies in some fine castings. The surface finish is a little fine. Again, for rock castings this usually isn't a big deal.
The "HYDROCAL® White Gypsum Cement" is the product I use most often for rock castings. It's much stronger in the "green" state than the hardware store plasters. That lets me make a copy out of each mold in less than an hour. It also has a finer surface finish that picks up the little details in a good rock mold. If you're using Woodland Senics rock molds this is over kill. The WS molds aren't that finely detailed. I mostly use molds from Bragdon Enterprises, which have a lot of fine detail and deep reliefs. Hydrocal White is noticeably better for this quality of a mold. When in doubt, this is the best plaster to try on a new project. It's also pretty inexpensive if you can find a local supplier that carries it in 50 or 100 lb bags. Your best bet will be a concrete supply house in an area with lots of historic homes. It's often used for plaster crown and ceiling moldings.
The "HYDRO-STONE® Gypsum Cement" is the best of the best when it comes to model railroad casting plasters. It has the highest surface finish with good "green" strength. I use Hyro-Stone when casting tunnel portals or other man made objects where small imperfections in the surface are most noticeable.
The other plasters from US Gypsum are tailored for other application. Drystone is a quick set product often used for rapid prototyping and not really suitable for rock making. Hydrocal Statuary is very similar to Hydrocal White, but is modified to work better in hollow molds. It works fine for rock molds. Tuf-Cal and Tuf-Stone are fiber reinforces plasters. These don't work very well for rock castings. When you apply color washes to the rock surface the fibers tend to leave a fuzz on the surface. The other three on the USG site (USG #1, USG Molding/Casting, and White Art Casting) all have a surface agent that helps paint spread on the surface rather than quickly absorbing into the plaster. This is great for molding things you want to paint, but it makes it more difficult to apply color washes on rocks that need to soak in.
Styrofoam works much better that plaster or hydrocal. You can apply plaster to the Styrofoam too. I use texture paint instead.
The terraform is a lot less weighty and can be rearranged or cut faster and easier.
The terraform is a lot less weighty and can be rearranged or cut faster and easier.
Greg, I used hydrocal which I purchased from Ebay. It comes from a supplier in Pennsylvania named Robert Forrester products. 20lbs of product for $20 & free shipping.
George
George
Dave,
Thank you for taking the time to post such a detailed response.
(I have printed it out for future reference)
Thank you for taking the time to post such a detailed response.
(I have printed it out for future reference)
quote:Originally posted by bob3:
Dave,
Thank you for taking the time to post such a detailed response.
(I have printed it out for future reference)
Yes, actually useful information.
I buy 100 lbs bags of Hydrocal and use it for the rough shape of my mountains. At this point in construction I'm looking for strength. Then I make my castings out of plaster from Home Depot. Plaster takes paint much better than Hydrocal. Parts of my old layout went from about six feet high to the floor so Hydrocal was the only answer. Plaster can fail from it's own weight in large areas. Don 
quote:I buy 100 lbs bags of Hydrocal ....... Plaster can fail from it's own weight in large areas.
I might need a single bag to do all my scenery.....
I must say, this concerns me. This section is 4' tall by about 5' long. Im beginning to think after a couple of practice casts pictured below, I should reinforce with plastic poultry netting. Any thoughts, its already wrapped in plaster cloth.
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[/IMG]quote:Thank you for taking the time to post such a detailed response.
(I have printed it out for future reference)
quote:Yes, actually useful information.
Thanks bob3 and mwb. It's nice to know folks find the post useful.
quote:I must say, this concerns me. This section is 4' tall by about 5' long. Im beginning to think after a couple of practice casts pictured below, I should reinforce with plastic poultry netting. Any thoughts, its already wrapped in plaster cloth.
Greg,
That large rock face is going to take a LOT of plaster. The cardboard strips, even covered in plaster cloth, probably won't handle the load. I'd recommend getting a couple sheets of 1 or 1.5 inch polystyrene foam. Place the foam on its edge and build a series of stair steps in front of your existing plaster face. You can then use each stair step as a ledge to support higher rock molds. This will transfer the weight of each mold into a solid foam structure rather than cardboard strips. It will also give a little more natural slope to the rock face.
Greg, I think you need to support it perhaps at the level where the orange clamp is visible. Can you run a some wood supports behind the cardboard and then make another cliff from the orange clamp down? Instead of just one vertical wall face.
I personally didn't like the plaster cloth. Try covering it with Heavy Duty construction paper and papertowels soaked in plaster laid overtop.
George
I personally didn't like the plaster cloth. Try covering it with Heavy Duty construction paper and papertowels soaked in plaster laid overtop.
George
Dave and George, thanks for the ideas. I think some bottom support will be the key to carrying the weight of the castings. Some of the challenge with building out to far from the wall is the 30" trestles. I wanted the trestles to rest entirely on the valley floor and not into the vertical rock wall. I have the same condition on the front wall except I was able to keep the track much further from the wall which should simplify things. I decided to attack this more challenging side first to work out the bugs on the front valley which will be more of a focal point. Here is a photo with the trestles mocked up to give you an idea of whats happening.
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gregj, I would simple cover it in Hydrocal for strength, then put your castings on. This area of my old layout was done that way and was very strong. Hope this helps. Don 
quote:Originally posted by GEF:
Greg, I used hydrocal which I purchased from Ebay. It comes from a supplier in Pennsylvania named Robert Forrester products. 20lbs of product for $20 & free shipping.
George
Thanks for the awesome tip, bought 40lbs for $38.00 w/free shipping.
Mike
A costly mistake
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I just could not stand the thought of loading up this frame with 80lbs of hydrocal only to have failure down the road. It would be like building a house on a poor foundation. I have decided to use 1" rigid foam supported below by a ledger board in which I will begin experimenting with ways to attach the hydrocal castings tomorrow.
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[/IMG] I just could not stand the thought of loading up this frame with 80lbs of hydrocal only to have failure down the road. It would be like building a house on a poor foundation. I have decided to use 1" rigid foam supported below by a ledger board in which I will begin experimenting with ways to attach the hydrocal castings tomorrow.
greg, I piece my molds together and try to fit them as close together as I can. I simply put a gob of joint compound on the back of the mold and push it in place. The compound that comes out the sides of the mold will fill in any gap. Wipe of the extra compound and when it's almost dry you can detail it to match the mold. Don 
Don,
Will your method work attaching them to foam board? I was going to try using polyurethane tube glue to stick them on the foam. I haven't found to many materials that this glue would not adhere together.
Will your method work attaching them to foam board? I was going to try using polyurethane tube glue to stick them on the foam. I haven't found to many materials that this glue would not adhere together.
Greg,
When applying your rock castings to a near vertical surface, consider using long nails pushed into the foam as temporary supports while your glue sets. I usually squirt some acrylic latex caulk compound on the rear of the castings and then use Sculptamold between castings to anchor everything in place. This works whether the support base is cardboard strips/plaster or styrofoam.
I think your original support system would have been fine with an extra layer of Hydrocal or Structolite applied over the plaster gauze for additional strength. Sorry, I didn't catch this thread in time to maybe save your original hard work. But that is going to be a great scene and worth the effort.
This scene is supported mostly by cardboard strips and a good thick (1/4"+) layer of Structolite over plaster gauze. It has survived over 10 years worth of being leaned by visitors as well as myself.
Jim
When applying your rock castings to a near vertical surface, consider using long nails pushed into the foam as temporary supports while your glue sets. I usually squirt some acrylic latex caulk compound on the rear of the castings and then use Sculptamold between castings to anchor everything in place. This works whether the support base is cardboard strips/plaster or styrofoam.
I think your original support system would have been fine with an extra layer of Hydrocal or Structolite applied over the plaster gauze for additional strength. Sorry, I didn't catch this thread in time to maybe save your original hard work. But that is going to be a great scene and worth the effort.
This scene is supported mostly by cardboard strips and a good thick (1/4"+) layer of Structolite over plaster gauze. It has survived over 10 years worth of being leaned by visitors as well as myself.
Jim
greg I don't know. Might not. After I framed the mountains to a general shape I covered them with "Black Wrap" for a rock shape and next covered with Hydrocal. It's strong and very light. Black Wrap is available here: http://www.filmandvideolighting.com/blstforo12.html
It's like tinfoil but much stronger and is flat back. We use Black Wrap in lighting for TV. Comes in 50 ft. rolls for about $20. I think I'm the only person I know that uses it but it really great stuff. I build a frame of wood and criss cross it with the stuff. It holds it shape. I crunch it up then pull it back out and place it on the frame. Any questions just write me. Don
It's like tinfoil but much stronger and is flat back. We use Black Wrap in lighting for TV. Comes in 50 ft. rolls for about $20. I think I'm the only person I know that uses it but it really great stuff. I build a frame of wood and criss cross it with the stuff. It holds it shape. I crunch it up then pull it back out and place it on the frame. Any questions just write me. Don
Hi Greg,
Jim's suggestion to use nails as temporary supports is excellent. Since you're going with a foam base I would suggest using drywall screws instead of nails. The large threads get a good bite in the foam.
I also suggest using polyurethane foam to glue the castings to the sheet foam. Squirt a little foam on the back of the casting, smear it around to cover the back surface, and then place it on the rock face. The foam will expand to fill the space between the sheet foam and the rock casting. Use the foam sparingly or it will over expand and push the castings away from the base. Polyurethane is one of only a few materials that adheres well to both polystyrene foam and hydrocal. This mountain was built with the method I described above.
Jim's suggestion to use nails as temporary supports is excellent. Since you're going with a foam base I would suggest using drywall screws instead of nails. The large threads get a good bite in the foam.
I also suggest using polyurethane foam to glue the castings to the sheet foam. Squirt a little foam on the back of the casting, smear it around to cover the back surface, and then place it on the rock face. The foam will expand to fill the space between the sheet foam and the rock casting. Use the foam sparingly or it will over expand and push the castings away from the base. Polyurethane is one of only a few materials that adheres well to both polystyrene foam and hydrocal. This mountain was built with the method I described above.
Thanks for everyone's insight on this project. It gets easier as I figure out a system for building this scene. I did switch to Plaster of Paris after running out of Hydrocal twice. I like the Hydrocal, it mixes better it's stronger and though it's a bit heavier it seems a little smoother. On the other hand it's more expensive and not as readily available as PoP and I have a lot of mountains to do. Below is a pic shot with my iPhone, not the best but you get the idea. I'm very pleased with the results.
As you should be, that looks really good. So how or what are you using to color them? Again very good work...
Thanks Chris, I really value the input of the talent on this forum. I am using Windsor and Newton tube acrylics from AC Moore. The specific colors I used to achieve this are titanium white, raw umber, yellow ocre, raw sienna and ultramarine blue. I am using cheap brushes and often dilute the colors down with water to get into all the nooks and crannies. The base color is t.white, raw umber and yellow ocre which makes a yellowish tan, I then follow up with raw sienna for reddish tan highlights, and ultramarine blue to get a bluish gray color. Using straight raw umber will give you more of a brownish look and really accents cracks and deep spots. Painting wet on wet allows you to blend colors much easier too. Sorry for the book.
Greg, they look great! Can't wait to see the finished project with the Trestle. When your done with those rock molds, I would like to borrow one to try it out. Hopefully they get some use on TrainPops layout someday.
George
George
quote:Originally posted by gregj410:
When I go to the USG site for Hydrocal I find 9 different casting products. Can anyone say specifically which one I should use for casting a rock face?
I used US GYPSUM ..HYDROCAL WHITE when i was making Tom Yorke O scale kit re-issues Its pretty strong and dries white. It carves easy also when wetted with damp cloth.
Using a clean margerine container or similar and using a mix ratio of 2 parts hydrocal to one part cold water. Use wifes proper cup measuring tools. Place hydrocal into container first then pour water in........wait and watch while the plaster/hydrocal gets slaked completely with the water and then begin carefully mixing using a metal fork, WITHOUT WHIPPING the hydrocal. Using a large spoon try to remove as many bubbles on the surface as possible. NOTE... hydrocal sets up fairly quickly and you do not have a lot of time...so be quick !! If pouring into a mold make sure the mold has first been sprayed with a mixture of a very small amount of dish wash detergent & water, then rinsed with cold water, this is too reduce the surface tension in the mold.
your item should be ready to be removed from a mold in 2-3 hours or more. It will take 1--3 weeks for the part to air dry and remove as much moisture as possible. DO NOT place your part in an oven.......Tom Yorke told me it makes the hydrocal extremely brittle and changes the molecular structure of it ?
Do not dump or rinse the mixing parts in a sink, otherwise you might be calling the roto router guy.
mike
quote:Originally posted by gregj410:
Thanks Chris, I really value the input of the talent on this forum. I am using Windsor and Newton tube acrylics from AC Moore. The specific colors I used to achieve this are titanium white, raw umber, yellow ocre, raw sienna and ultramarine blue. I am using cheap brushes and often dilute the colors down with water to get into all the nooks and crannies. The base color is t.white, raw umber and yellow ocre which makes a yellowish tan, I then follow up with raw sienna for reddish tan highlights, and ultramarine blue to get a bluish gray color. Using straight raw umber will give you more of a brownish look and really accents cracks and deep spots. Painting wet on wet allows you to blend colors much easier too. Sorry for the book.
Ahhh o.k. that is a good idea. Well again I think it came out great, the color looks very good. I like the streaking/highlights it adds to it...great job keep the pic's coming....I'll be looking for more....
Well done Greg!
Looks like you're off to a great start. I'll look forward to seeing the results.
Looks like you're off to a great start. I'll look forward to seeing the results.
How do I find Structolite? I went to Home Depot (Deteroit area) and no one knew anything about it. What section is it in? What is it used for?
To change the topic a little but it is still relevant. When you stain various plasters with thinned acrylics remember that the harder or denser the plaster, the rate of stain absorbtion is different. This can be a problem trying to match castings with fill material in the joints. While it is soft and requires a good base I like dry sheetrock mud. I usually use the 45 minute setting version. Mix it your self with water and it drys fairly quickly. Pre mixed uses a glycol base and takes a lot longer to dry.
Hope this is of interest.
George Lasley
Hope this is of interest.
George Lasley
I use Hydrocal just for my rock castings, and USG 18Lb Bag Easy Sand 20 Minute Joint Compound Powder for the rest of the scenery. It gives the same results with a lot of working time.
...keep the rails polished...
...keep the rails polished...
Yes USG plaster is best, but most plasters fine. The big thing is mixing, rule of thumb, put water in mixing container add plaster till fills from bottom to top of water. Once the plaster fills to surface this will correct amount. Mix with drill and mixer, plaster of paris is very fast. USG materials can be purchased for different hardness and set times. I like hydro-stone. Next you need good molds, and spray them with soapy water before poring
plaster into them. Demold depends on set up but usaully 1-2 hours. I found once castings dry 2-3 days quicker if fan on them they can be attached to foam, wood, chicken wire etc with construction urthane adhesive found at HomeDepot. I fit them together and fill spaces with drywall compound. This be textured and worked nicely
and reworked once dry. Paint in latexes and add static grass or textures desired.
Just takes practice and a good eye. See altoonamodelworks to contact me.
Bob Spaulding
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