# Casting walls



## Paulus (May 31, 2008)

I made this mold out of styrene last week. It's the idea to use it to cast viaduct retaining walls out of a Portland cement / sand mix.









More pictures of making the mold can be find at: this photo album. 
A piece of hardware cloth is cut is shape to give the cast some extra strength.









The first casting did not came out very good. I used a mix of Portland cement and black earth (about 50-50). The error I made was that I forgot to 'oil' the mold before the casting, so the casting sticked inside the mold to much and it was hard to get it out right.









A second casting was made (on september six as you can see). This time lesser earth and more Portland. And I sprayed silicone oil in the mold before casting!!









And this time it came out real nice! ;-)

















But later turned out that the mixture was not right. Wile the first casting dried up well, the second showed cracks in it when dried. 









I filled up the cracks with new cement. Lets hope this give it some more protection and some more strength. Also I 'painted' the cast with thinned white PVA glue to make it more water resistant (following the late Peter Jones PVA glue philosophy). Actually, the layer of PVA glue can best be applied when the casting is still a bit wet. 











Today I made the third casting. This time I used a mixture with about a 60-40 mix Portland and earth. But I made the mixture a bit thicker/less wet. With the first two casting the mixture could be poured in the mold, but now it's more paste like (see the blob of mixture at the right bottom). I had to stuff up the mold with the mixture instead of pouring it in.First I laid a "bottom", than placed the hardware cloth in and cover it with a next layer. 










That's all for now! The third casting is laying in the sun to dry (or can I perhaps better place it in the shade to avoid too fast drying???). 
I must say it's relatively easy to cast the walls. Finding the right mixture is a second thing but I think I'm close now. I'll post some pictures of it when it comes out.

Meanwhile, there are more pictures of the process described above in my photo album on Fotki. 

Paul


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## flats (Jun 30, 2008)

I have used 60/ 40 but it was sand mixed with it, I also found that a heaver wire 
cloth holds it together better, also let it dry in a cooler place. In the summer I 
sprayed fine mist of water on the casting. My walls and tunnel portales have been 
around now for 10 years and still holding up with no cracks. 

Ken owner of K&K the road to nowhere


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## Paulus (May 31, 2008)

Thanks Ken! I was in doubt of the drying but now I removed my casting out of the sun and put it in the garage to let it dry slower.


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## kormsen (Oct 27, 2009)

if you put your cement in the sun to dry, you sure will get cracks. 
let it cure in the shade. if it dries too quick, moisture it, to dry slower. 

(btw - your first try looks nicer to me, than the second. like a rugged weathered old wall)


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## Lawrence Wallace (Jan 2, 2008)

Paul, 

Try using "Pam" used for cooking as a mold release. 
It has worked real well for me. Just make sure when you are finished for the day you was it with detergent to remove any residue from the "Pam", as it will get sticky as it dries out. 

You are using what we call "Chicken wire" here. I use !/2" "Hardware Cloth", "The bottom of the Rabbit Cage" stuff, it's heavier and gives more support. It can be pushed down into the concrete with out bending out of shape to much. 

To remove air bubbles I tap the mold on the table a few times. 
Putting a slight taper to the mold sides makes removing the casting easier and is barely noticeable in the finished piece. 

In construction work concrete is kept damp to promote curing. After removing the cast piece from the mold, a fine spray will do for a couple of days, don't over due the spray the first time after the casting sets up. 

Concrete continues to cure over a long period of time.


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## John J (Dec 29, 2007)

I remember in California years a go they covered the cement on the freeway with used carpet. They they would wet the carpet to keep the concrete moist slowing the drying porcess.

What about a old bath towl on your casting to slow it down. 

JJ


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## SteveC (Jan 2, 2008)

After setting up and being removed from the mold, keep it out of direct sunlight better yet in a shed/garage cover it with plastic and check it periodically and if needed using a spray bottle adjusted to a fine mist keep it moistened.

I know the following information for structural concrete isn't the same as what you are using, however, it acquires its maximum compressive strength at around 26-28 days, and its kept moist for that length of time.


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## Ross (Jul 19, 2009)

Been thinking about making some walls myself BUT out of that air drying clay that is available (Giotto) - (Similar available for oven drying as well). 
Seems less hassle and seems, so they say, to stand up to outside weather. However, wonder if it will stand up to freezing weather? after all, terracotta flower pots seem to stand up to it (well, some of them!). 
I'll have to give it a go and will hope to report back. 
Big job..engine house for 2 Porter 0-4-0 ST's. Footprint is approx 25" long by 18" wide. 
Chickened out of one for a 3 truck Shay and an Annie! 

Must say..myLargescale..what a great website. Cheers fellas.


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## Spule 4 (Jan 2, 2008)

Yes, Steve is right. Concrete CURES better when wet. The term "dry" is not correct, it gets hard via a chemical process, not actually "drying" out.


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## Greg Elmassian (Jan 3, 2008)

We usually call that wire you have "chicken wire"... It's very fine and I don't think it adds much to your strength. I would actually find some real "hardware cloth", which is typically a finer mesh (comes in various sizes) and is a square weave, thus looking just like cloth. 










Regards, Greg


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## Gary Armitstead (Jan 2, 2008)

Paul, 

In my "other life" before retiring, I was a die sinker making forging and press dies. We needed to take plaster casts (used hydrocal) of the dies, for checking and inspection of the part. We always used plain, old lard or Crisco. We wiped the excess lard away leaving a very thin coat. Then use a cheap paint brush to spread and smooth the remainder. The last thing you apply as a parting agent is BABY POWDER. Put it in the mold and spread carefully using a clean brush (dedicated for spreading the powder ONLY). ONLY use the brush to do this! DON"T smear with your fingers or any other object. GENTLY blow the excess away using a can of air. We were able to get casts this way and still have ALL the detail show including part numbers and lettering (some only .005" to .010" deep) without losing any detail. I know this will work for you and you will be very pleased with the detail you get on your walls. Just ask if you have any questions about this technique. 

As to the cracking, you need to let your casting set-up in the mold in the shade out of the sun. KEEP MOIST. The casting will set-up by chemical reaction, not drying it out. Put your hand on the casting during the set-up time and notice the amount of heat generated. That's because of the reaction taking place during the set-up and curing process. Good luck. They will make beautiful wall castings!


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## John J (Dec 29, 2007)

Posted By Gary Armitstead on 11 Sep 2010 01:01 PM 
Paul, 

In my "other life" before retiring, I was a die sinker making forging and press dies. We needed to take plaster casts (used hydrocal) of the dies, for checking and inspection of the part. We always used plain, old lard or Crisco. We wiped the excess lard away leaving a very thin coat. Then use a cheap paint brush to spread and smooth the remainder. The last thing you apply as a parting agent is BABY POWDER. Put it in the mold and spread carefully using a clean brush (dedicated for spreading the powder ONLY). ONLY use the brush to do this! DON"T smear with your fingers or any other object. GENTLY blow the excess away using a can of air. We were able to get casts this way and still have ALL the detail show including part numbers and lettering (some only .005" to .010" deep) without losing any detail. I know this will work for you and you will be very pleased with the detail you get on your walls. Just ask if you have any questions about this technique. 

As to the cracking, you need to let your casting set-up in the mold in the shade out of the sun. KEEP MOIST. The casting will set-up by chemical reaction, not drying it out. Put your hand on the casting during the set-up time and notice the amount of heat generated. That's because of the reaction taking place during the set-up and curing process. Good luck. They will make beautiful wall castings



Gary. What you discribe is like "flowering a cooking pan" When you bake cakes and Browines you greast the pan with cirsco then drop a cup of flower in it and spread it around to coate the sides of the pan. It acts like a release when you are done baking. 

That should work with the wall casting.

I wonder what would happen if you greased your casting then flowered it with dry portland cement.


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## Tenn Steam (Jan 3, 2008)

Great idea. 
When mixing concrete for small construction projects I was taught to mix one part portland cement to three parts sand and then leave at a thick consistency which could dump from a wheelbarrow but would stand up when dumped. 
Jig Stones molds recommends vinyl patching cement for their molds. Their website gives a lot of information for using their molds which I think would apply to you custom made molds as well. There is a list of what works and what does not based on experience of modelers. 
This will make a great looking wall if you can cure the crumbling problem. Please continue to post progress reports. 
Bob


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## SE18 (Feb 21, 2008)

Nice, 


Another technique to scratchbuilding one instead of cutting strips would be to carve the lines in wood or styrene, then pour RTV inside and use the RTV as the mold.

Cheers 


Dave


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## Paulus (May 31, 2008)

Thanks for all the good advice on this guys! 

I kept the third casting more wet and it's drying now without any cracks. I have to learn to be patient now it is not drying in the sun anymore ;-)
But the result is indeed much better! 


I had to surf the internet to understand some of the other mentioned solutions (I'm an European, so not all brands and terms are directly clear for me). While surfing I came across some funny things (like Crisco, that looks like in my country is only for sale in some very specialized cooking shops and .. euh.. some other "specialized shops" so to say and you _don't _want to know where they use it for...- No links, this is a family site!-). Very pricey in both kind of shops. I have to look for an European variant of it. Is Crisco some kind of grease/Vaseline or more like butter? 

Lawrence, PAM is that the olive oil in a spray can? (Like this: http://www.bodystore.nl/pam_cooking...ve_oil.jpg).
You and Greg are right btw about the chicken wire. And I was thinking I had the right thing! 

Thanks Greg for posting the picture of what is true hardware cloth! I had the model houses of Ray Dunakin in my mind and thought this was the stuff he used. When checking again I see Ray also used the square mesh you showed in the picture. I think I'll buy some of it when I visit the DIY store next weekend again.

Gary, baby powder, I do still have that standing somewhere! With my youngest turned 7 years last month I guess I can use it without SWMBO has objections... 

For the 4th casting I guess I go for a silicon spray grease layer and than "flower" it with babypowder. Would that work you think? 

Bob, thanks for the advice on the JigStone website! I'll check the suggested mixes and see what works. 

Dave (EDIT: I wrote the wrong name the first time, sorry!!), no RTV but I have a bucket of molding latex in stock. I'm thinking of making a latex mold of one of the castings and try that because the styrene mold is getting damaged a bit (the plastic strips come loose and one of the sides has to be glued back again). 





Thanks again all for all your suggestions and input! I post some pictures of the third cast soon.

Paul


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## Paulus (May 31, 2008)

Almost forgot to mention: I'm planning to try also the "Hypertufa" mix, see; http://www.the-artistic-garden.com/hypertufa-recipes.html
I don't know if it will work to cast in this mold but I've seen some very beautiful results with this stuff! I know the former G-Scale Mad member "Graniteshop" (also registered on MLS) did some awesome landscape building with it. It's much lighter than concrete.
I ordered a 100 liter bag of Perlite (what is hard to get here) and can't wait to experiment with casting or at least make some rocks, roads, walls etc with it!!! ;-)


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## Spule 4 (Jan 2, 2008)

Crisco is a vegetable based lard. Has well known cooking and "other" uses as you found out. Bakvet or bakers fat I think would be the proper Dutch term? 

Yes, Pam is no stick cooking spray.


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## Paulus (May 31, 2008)

Thanks Garrett! Bakvet is indeed a Dutch term, or more correct: "frietvet" because It is used to fry french fries (that we we call "friet"). So, I can search for the vegetable kind of that.


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## Paulus (May 31, 2008)

OK, here are two pictures of the third casting. I kept it wet and shady and it looks very nice. No cracks at all. When I took the casting out of the mold I went over it with diluted PVA glue directly. 
The brush softened the lines of the stones, so the stones don't look all the same and the wall gets an older appearance. 























Paul


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## Gary Armitstead (Jan 2, 2008)

Very nice Paul.


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## SteveC (Jan 2, 2008)

Nice job Paul.


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## SE18 (Feb 21, 2008)

Nice work! 

I've cast hypertufa bricks (in a brick mold). They're not as strong as regular bricks made of mortar or cement but they do hold up; I'd increase the ratio of cement in the mixture of hypertufa to be safe or glue the brick wall to hardiboard

Dave


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## Paulus (May 31, 2008)

I placed one of the walls in postion. Leveled it with Hypertufa.Perhaps I go over the Hypertufa with the Portland mix used for the castings and carf stones in it.


























Paul


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## Ray Dunakin (Jan 6, 2008)

That wall turned out great, Paul!


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## takevin (Apr 25, 2010)

yes it did, very well done!


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## Paulus (May 31, 2008)

Thanks guys! 
BTW Ray, your castings on your Dos Manos buildings inspired me to try this!!!


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## John J (Dec 29, 2007)

Your wall turned out great. I like the last picture very much.


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## Biblegrove RR (Jan 4, 2008)

Super nice job!


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## Nicholas Savatgy (Dec 17, 2008)

OOOOOOOOOOOOOOOOO These came out sweet looking, nice work.


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## joe rusz (Jan 3, 2008)

Very nice job. Could work on walls, I'll bet.


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