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Using Hydrocal in a Landscape

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Using Hydrocal in a Landscape
Posted by JIM ROHRBACH on Monday, September 17, 2018 6:39 PM

Hello,

I'm creating a diorama and used cardboard webbing with a plaster cloth overlay that turned out looking like a large waffle.  I then spread Sculptamold over that, which hid the waffle look but isn't too smooth.  I'm considering pouring a thin layer of Hydrocal over the Sculptamold so level and smooth out the overall look.  I've read some previous posts and saw the suggestions of using Plaster of Paris since I already have the "hard shell" but I already have the Hydrocal and may as well use it.  Can I just mix a small amount and lay that over the Sculptamold and continue until the whole landscape is covered?  This is the first time I've done this and I don't want to muck it too badly.  Thanks for any help!

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Posted by carl425 on Tuesday, September 18, 2018 12:47 PM

Unfortunately, the waffle look is caused by screwing up the first step of the process - the cardboard web.  Chalk it up to experience and start over.  Put the pieces of the web closer together and stretch the plaster cloth tighter.  Some folks use masking tape or drywall tape (the plastic grid type) on top on the web to help prevent the waffle effect.

I have the right to remain silent.  By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.

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Posted by doctorwayne on Tuesday, September 18, 2018 1:38 PM

Since you have the Hydrocal on-hand, it sorta makes sense to use it.  However, for my pace of doing such work, it hardens much too quickly. 

I used Durabond 90 for all of my scenic landforms, applying it over aluminum window screen stapled to the open grid benchwork, with additional risers where necessary.  The "90" in the name refers to the approximate setting time, in minutes, but it's also available in 20 and 45 minute setting times.
All versions can be mixed to various viscosities, and will harden in approximately the specified setting time.  Once hardened, it is very hard, and difficult to sand - not normally a requirement for scenery.
Here's a partially finished area of my layout...

I originally tried to paint it with interior latex house paint, and while do-able, it was time consuming and labour intensive.  Instead, I thinned the paint about 50% with water, and applied it as a stain - extremely fast and easy, and all of it will eventually be covered with other scenic materials, like this...

The resulting structure is also very strong, and in areas where the layout is deeper than usual, I can stand on a stepstool and reach in, supporting most of my weight with one hand directly on the landforms, in order to reach areas otherwise inaccessable.
I use Durabond to cast rock features in Woodland Scenics rubber moulds, and also use it to create water scenes...

The latter are all done atop well-supported 3/8" plywood, with the Durabond "worked" to create ripples and "white water" effects.  Application is about 1/8" thick, and when set, is painted with standard flat, indoor latex house paint.  When dry, the "water" gets three coats of water-based high gloss clear urethane.  Cheap, easy to do, and easy to clean, and very durable.
I also used it to cast the bridge piers and abutments seen in the photos.


Other than the choices of working times offered by Durabond, I'd guess the lower cost of Durabond vs Hydrocal are the main advantages of the former.  Dental plaster, similar to Hydrocal, is another option, but also expensive.

Wayne

 

 

 

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Posted by MisterBeasley on Tuesday, September 18, 2018 1:42 PM

The cardboard grid makes a giant waffle, but the plaster cloth makes a fine grained waffle.  Which have you got?

I prefer Gypsolite for this, because it gives me a rough, gritty texture that looks more natural.

It takes an iron man to play with a toy iron horse. 

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Posted by BigDaddy on Tuesday, September 18, 2018 1:43 PM

I don't think the hydrocal will hurt the scultpamold.  Doesn't sculptamold have plaster in it?  If you don't want to start over, you don't have to.

Wearing a latex glove and keeping it wet will help smoothing either sculptamold or hydrocal.

Henry

COB Potomac & Northern

Shenandoah Valley

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Posted by riogrande5761 on Tuesday, September 18, 2018 2:26 PM

No wafflle effect here but I went a little crazy with the cardboard strips using them to create the land form as I moved from right to left:

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by RR_Mel on Tuesday, September 18, 2018 2:42 PM

Everything mentioned above works very good and I did it the same as Wayne for over 50 years with great results.  I started my current layout using the same technique as Wayne but I happened to run across a large quantity of 2” x 12” x 18” Styrofoam blocks.  I used Styrofoam glue in the calk type dispensers and layered the blocks, some up to 34” high.  I used a hotwire cutter to form a rough contour then used Plaster of Paris rock molds to make my mountains.  The foam is very strong and extremely light, I used the same material for rolling hills too.
 
Here are a few pictures of my Styrofoam based scenery.
 
 
 

 
The picture above is adding the Plaster of Paris rock castings to the Styrofoam blocks.  Messy working with drippy Plaster of Paris but looks so good when its finished.
 
 
 
Mel
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by j. c. on Tuesday, September 18, 2018 7:04 PM

while i no longer use hard shell( gone to shaped foam) , when i did i used 3/4 inch chicken wire as a base and old bed sheets dipped in hydrocal , resulting in a thin(at the most 1/16 or 3/32 of an inch thick) strong light weight  and tough covering. 

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Posted by G Paine on Tuesday, September 18, 2018 10:59 PM

Plaster cloth usually ends up with a waffle like surface, and Scuplamold has fibers in it that can leave a rough surface. Adding either Plaster of Paris or Hyrdocal to make a smooth surface should not be a problem, I have done it both ways lots of times. I prefer Plaster of Paris because it is easier to drill into to plant trees or otherwise modify. Hydrocal dries rock hard, so it is hard to modify or carve.

George In Midcoast Maine, 'bout halfway up the Rockland branch 

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Posted by JIM ROHRBACH on Wednesday, September 19, 2018 4:37 PM

Thanks for the input, Carl.  As I said in my initial post, the Sculptamold has already been layered over the cardboard webbing and plaster cloth the the Sculptamold finish is rather rough, hence the need for the Hydrocal.  If I ever do this sort of thing again, I'll pay more attention to the webbing spacing to do away with the waffling.  Thanks again.

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Posted by JIM ROHRBACH on Wednesday, September 19, 2018 4:50 PM

I made the mistake of spacing the cardboard grid too far apart when I installed it.  I did not know I could smooth the Scuptamold as I was installing it in the first place.  I watched a lot of MR Video Plus to see how it's done but didn't see how smooth it was when finished.  Oh well! 

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Posted by riogrande5761 on Friday, September 21, 2018 12:20 PM

Sculptamold may not be necessary; ordinary plaster of paris can hide waffle effect as long as the cardboard strips are not really far apart.

Here is the cardboard subscenery in with strips put in with hot glue.

Here is the area now with plaster of paris.  It's pretty hard to see any waffle effect:

Same area now with colored sanded grout to add color and texture.  A bit of ground foam and some scrub brush as well.

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by BigDaddy on Friday, September 21, 2018 6:01 PM

riogrande5761
Here is the area now with plaster of paris. It's pretty hard to see any waffle effect:

I don't seem to know how to copy pictures in my quote, but your picture is there.  35 years ago, using hydrocal and paper towels that spacing gave me waffles.

These days using plaster roll, can you guys achieve a flat area, if you wanted the area above closest to the aisle to be flat for building placement, is that achievable?

Henry

COB Potomac & Northern

Shenandoah Valley

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Posted by doctorwayne on Friday, September 21, 2018 6:48 PM

BigDaddy
...if you wanted the area above closest to the aisle to be flat for building placement, is that achievable?

You could probably do it using plaster, but most of my structures sit atop a suitably-sized piece of plywood, supported on risers attached to the open grid benchwork.  The plaster-on-screen landforms are then added, with the screen also stapled to the edges of the plywood "building lot". 

For a town or street scene, I'd do most of the structures and their surroundings atop plywood, as you can always add lawns and other needed ground cover, along with trees, without having to use plaster.

Wayne

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Posted by BigDaddy on Friday, September 21, 2018 6:57 PM

My layout 35 years ago was cookie cutter plywood and I did not give any thought prior to construction for flat "buildable areas"  I think I put sheets of cardboard on top my waffle and covered those with plaster.

Now I am working with foam, and flat is no problem.  Creating postive and negative elevation is more challenging.  Let me rephrase that, creating smooth positive and negative grades is more challenging. 

Henry

COB Potomac & Northern

Shenandoah Valley

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