Liquid foam?

[slawsonb]

A stupid newbie question. Does anyone use a liquid foam, like the expanding stuff used for insulation, for making the lost foam mold?

Bruce

[nashyboy]

You could use the expanding foam but i'd advise against it (unless you cast very small pieces - in a well ventilated area). I beleive some of the expanding foams are polyurethane based - when they are sprayed they have some pretty nasty fumes (Isocyanates, formeldyhide etc), when they burn away, they release similarly bad stuff. I am not 100% sure if all expanding foams are the same, just make sure you are absolutely certain of your product BEFORE you use it.

Hope this helps.

[Geof]

A stupid newbie question. Does anyone use a liquid foam, like the expanding stuff used for insulation, for making the lost foam mold? Bruce

No such thing as a stupid question. Asking a question before doing something that could have unpleasant consequences is smart.

Only use the expanded polystyrene foam for lost foam casting; as nashyboy mentions the expand-in-place stuff releases nasties when being used and worse when it is burnt.

[slawsonb]

Thanks for the advise guys.

Do you have any recommendations for any expanded polystyrene suitable for home use?

Bruce

[Geof]

There was a thread a while back about using the blue insulation foam used in building. I suggested it would not be suitable because it probably contains fire retardants. Another person said they had used it and it worked but produced a lot of fumes.

[nashyboy]

FOR ONE_OFFS: The easiest way (although a little inaccurate) would be to purchase a block of polystyrene and manually shape or carve it using a cnc (or manual) hotwire or fastwire machine. Of course you will find it hard to make a perfectly smooth surface but it all depends on what you are intending to cast.

Expanded polystyrene is quite simple to use (bombard styrene with steam inside a mould and it expands) just add bonding agent to make it stick together. The only problem is - you need a very strong mould as there is quite an amount of pressure applied by the expanding foam - this would only really be practical if you were making thousands of casts. If you still want to use it (I'm not trying to talk you out of it in any way!) I'd suggest you visit a local polystyrene factory in your area, I am sure you'll find someone who's more than willing to show you the ropes and maybe even supply you with the required materials.

[slawsonb]

Thanks. Looks like I'm better off using other methods.

Bruce

[nashyboy]

Have you considered wax moulding?

[slawsonb]

Have you considered wax moulding?

Actually, no I haven't. Can it produce as nice a finish as texture coated foam?

Bruce

[spunky1974]

Here's a thought. What about the water based kind. Here is the MSDS PDF...........

http://dap.com/docs/msds/77344.pdf

[nashyboy]

Your quality of finish really comes down to what material you are going to use for moulding. If you are plannig to use sand moulding, your finish quality will not be excellent, but you can get different grades of sand from course (really rough) to fine (not so rough). If you are planning to make high detailed items, you can make the mould from several different materials (following are just a few) plaster of paris, refactory material or even some resins these days that are designed to handle the temperature from low melting point metals.

To explain how the wax method works (investment casting I think is the correct term), you make a model of the item you are wanting to make, then add flow lines, in gate, out gate, etc. Then you wrap the wax with your chosen mould material. When the mould is dry, you heat up the whole mould which melts the wax out, then you have your mould ready to go.

If you would like any more info, pm me and I can forward some literature to you about some different methods.

Thanks

[WayneHill]

Hmmm.. déjà vu

Great Stuff expanding insulation for lost foam molds?