Molding

[Vulcan1]

I wanted to ask some questions and I think this is the place. :) I read another post but did not see an answer on it. Somebody mentioned Hydrocal and I have looked for it but cannot find it. I have used bodyfill and plaster of paris for making some molds but I have a problem with the smell and also the cost with the bodyfill. The plaster works but if you need a larger mold it takes a long time to dry. I left this one for 2 days and on the 3rd day stuck it in the oven for 3 hours at 300. Let it cool and when I took it apart it was still damp inside. I would like to try the hydrocal for the intakes on my clunk.
Any other comments would be appreciatted. :wink:
John

[nony]

John, they use it (or used to use it) for scenery for model railway layouts, so you can find it in train hobby shops if you get stuck.....

[Dave Holmes]

Sorry John, I saw your post and got distracted and did not respond.

It is available at hobby shops that cater to model railroaders, and at some building supply stores. The hobby shops usually buy it in 25 or 50 pound bags and break it down into one gallon buckets, or small bags. Last batch I got (and am still working from) was picked up by a friend of mine and he brought it over in two 5 gallon pails. I don't know which building supply store he wnt to, but it was somewhere in Mississauga. I'll try to get more details.

The LHS would be much more expensive on a per kg price, but if you only want a small amount, it's the route to go.

A few pointers on using it:

- It sets up as a result of a chemical reaction, and is exothermic (gives off heat)
- Setup time will be affected by heat, relative humidity but not as much by the consistancy of the mix. You can mix up a real soupy batch, let it sit and it will set up hard in the bottom of the container, with excess water sitting on top. (It will seperate out.)
- Use CLEAN utensils when mixing it. Mixing up a batch in a margine tub that has the leftovers of a previous batch will result in accelerated setup. I have a rubber spatula and a cheap (dollar store) stainless steel bowl I use.
- Once it starts to set up, you cannot do much with it but let it go. Adding water to thin it will only result in a crumbly product.
- I have taken moulds from canopies and did not use a mold release agent of any kind. If you want to, you can use a squirt of PAM or similar product which will not damage the plastic you are copying from.
- Once it is setup, and allowed to cure a bit, it is hard as soft rock, kinda like really hard chalk. It can be carved, but slowly.
- It is strong. 3 or 4 layers of paper towelling soaked in a soupy mix of this stuff, and draped over a crumpled newspaper form and allowed to dry makes a self supporting shell very suitable for simulating terrain on a model railroad. It is inherantly heavy as well. (Let's face it, it is rock)

I hope this is useful info.

Dave

[Gary Maker]

Vulcan

I have a couple of boxes of this here in my stash of stuff for my N-scale train layout. If you can't seem to find any, let me know and I could send you a box if you'd like. Its in a box that look like a milk carton but would be about a liter and a half size. I believe the cost is somewhere around $12 but I can get the exact price for you from the model train store!

[Vulcan1]

Thanks for the answers :wink: When I get up to Calgary I will have a look. Iwould like to get a large bag of it to have on hand and I need to make some molds which are fairly large. For a parting agent I have a liquid and also a wax that should work. It is for making molds with epoxy and I still have lots. It sounds like the right stuff for me to use and where did the answer come from.(("Members of Rcanada")) A great place to be.
John :)

[JohnH]

From the description Hydrocal sounds very much like a hydraulic cement such as Kwikplug. Building supply stores would carry it or similar under a variety of trade names. It is used to plug running water leaks, set objects in concrete etc. I have used LePages floor leveller (called Poly Underlay) for canopy molds with great sucess. It sets quickly although it takes a long time to dry through in thick sections. No problem to vacuum form a canopy over it after a day. From a look here I see that the floor leveller is non shrink while the hydraulic cement expands as it sets.http://www.lepageproducts.com/products/detail.asp?catid=25&subid=126&plid=326 and for kwikplug http://www.lepageproducts.com/products/detail.asp?catid=25&subid=61&plid=324

[Dave Holmes]

From the description Hydrocal sounds very much like a hydraulic cement such as Kwikplug.

Not really. I have used Kwikplug and it is much courser, like sand. Hydrocal sets up smooth, like silk while hydraulic cement has a texture like fine concrete. Hydraulic cement also expands as it sets, Hydrocal does not. Hydraulic cement also has a much shorter working time, 2 to 3 minutes if I recall, while Hydrocal will stay fluid, depending on thickness of mix, temp and humidity, etc of beween 10 and 20 minutes. Also, there are different types of Hydrocal if you want to get picky, with different setup times. I have rarely had a choice of what to buy, so I just take what's available and work with it.

Dave

[JohnH]

Yeah, sounds like the hydraulic cement is a non starter. It's been a while since I used any (not for modelling) but I believe there are variations from brand to brand. I can vouch for the floor leveller from actual experience. The Lepage brand is very fine grained, doesn't shrink and doesn't scratch the sample being molded. There are some brands that contain sand and unsuitable for this purpose. Some sample molds are on my site shown below under "construction - simple vacuum forming" Picture 1. Picture 2 shows a mold a fellow made with some hobby shop stuff. I would rate it as considerably inferior to the floor leveller.

[Vulcan1]

Getting a lot of answers :wink: I was also talking to a lady who makes stuff for a different hobby and she reccomended the stuff they make casts from. Said I could get it here in town at the drug store. After I get off and my grandaughter finishs her nap we are going down to check. Also will goand check the floor leveling compounds.
John

[LEE]

I got a box of mould making plaster from home hardware. It was in a milk carton like container, and is readily available and relatively cheap.

[Vulcan1]

Lee,
I have a couple of boxes from Home. I think they where in a red box and if so it is plaster of paris. It works great on smaller parts but when you get around 2" or better deep it takes a long time to set. I am trying to find an alternative to it. My druggist said he didn't stock cast material and go to the hospital to borrow some. Will try on mon. since I know everybody up there. Used to be an emt and still have friends I hope. :)
John