"Mold release" for bondo?

I want to make a mold off a part, using Bondo to make the mold.

What can I apply to the part so the Bondo won't adhere to it?

I have another project I thought of about two minutes ago that would be doing the same thing with a plastic part.

So, anybody have any ideas for what to coat a metal and a plastic part with to make a mold using Bondo?

Thanks,

-Brad

 

Pam cooking spray works for fibergl***.

 

Most any lube should work or maybe some Alum. foil .

Retro Jim

 

WD-40, Pam cooking spray.......

 

Don't really need anything.......... that is the problem Bondo doesn't stick to anything......even when you want it to

 

brown parcel tape works great

 

PVA mold release from www.tapplastics.com
they also have a ton of mold making supply's

 

Any oil, grease, PAM. Something a little oily......

 

I have molded a number of parts--Buy a can of paste wax for wood floors. Put on a couple of coats with a dry rag and let it set up for about 10 minutes---don't polish it off. This works well for Bondo and also for fibergl***.

 

I'd put a quick prime and paint on it. That way you have a non porous surface to put your wax and parting agent on, that won't just absorb into the bondo.

 

I've always used duragl*** and some simple car paste wax, duragl*** is far more durable and wont break when trying to get it out of the mold.

 

I've used Simple Green cleaning concentrate in a cheap spray gun before and was pretty happy with the release. Do not dilute, use it as a concentrate then spray it on, let it dry, spray another coat, let it dry....repeat until you're comfortable with the thickness of the coating.
The nice thing about using Simple Green is that unlike using wax or oily mold release products, it washes off quite easily once you're done.

 

Brad54; what type of casting are you trying to do?

I did some casting by using wax, not bondo. Works good on certain shaped objects that allow a parting line to remove the wax mold. Get huge candles at your local flea market for dirt cheap.

For intricate parts with no way to get a parting line to split the mold, there is a two-part synthetic rubber, but it's very expensive.

 

I've used saran wrap and paste wax.

 

a light smear of vegitable oil ougt to do the trick

 

The ability of the bondo to 'let go' of the part has a lot to do with the surface of the part. If it is smooth and doesnt have any undercuts it will work. But I would use an actual mold release. Look in the yellow pages for your area and find a place that sells injection molding supplies or call a local molder and ask if they know of a place locally that sells silicone mold release. It's designed to help plastic parts come out of an improperly designed mold.
When we have engineering changes done to existing tools, the tool shop will often 'make a bondo' of the change, which means they spray the **** out of the steel with mold release and then press bondo into the changed area in order to see what the new geometry looks like. but without a lot of mold release it can be a pain to get it out.
There are several companies that make mold release, i know stoner makes a decent one.

Scott

 

Sounds like another use for KY jelly!

 

Being a former composites spe******t who has made many molds..... Highly recommend spraying with gel coat, sanding and buffing to a mirror finish, then applying 5-6 coats of meguires wax mold release. Then spray a coat of gel coat over the plug and do your fibergl*** layup (8 or so layers of mat). As long as you don't have any negative contours the mold will practically jump off the plug with minimal effort.

If you just try to make a mold off of rough body filler you may have a hell of a mess on your hands trying to get the mold off. The resin could settle into the grooves of the body filler and bond to it.

There are techniques for just applying mold release to the body filler but that's not my style....and the results are a little less than professional....but maybe for your purposes it's not that critical.

 

Being a current advanced composites company owner, I agee with drjones96. For a fast job with little drama, paste wax is your answer. Cooking spray and other lubricants may not cause fish eye on you, but just getting the material to lay where you want it can be an issue. Three coats of wax, allowing each to dry and buffing between each, works best. Don't use a lot, just a thin, well applied coat each time, and keep application swirl marks to minimum. Co****ly appplied wax marks can actually make a part difficult to get to release. If the part has much draft, wipe on and buff off in the direction you will have to remove the bondo cast from.
I would bet you aren't doing a project of the scope that you'd need to do the gel coat and resin thing though.
If you need to talk direct with someone about what you're doing, how best get it off what you are essentially casting with bondo, pm me and I'll send you my cell #.

 

Just a heavy coat of car wax or furniture wax. Tap it lightly when it dries with a rubber mallet and it will release.

Are you using it for a buck or a hammer form?

Here is one I made last weekend for a hammer form.

Made a wire form of the area, close counts, the bondo will capture the shape.



I added metal to the top of the wire form to capture the bondo and to add strength.


Then applied wax heavily over the area. Mixed up some bondo, spread it thick over the area and pressed in the wire form. Not all the way,I left it up about a 1/8'' so the bondo would capture the shape.





I hammered the metal over the hammer form and it held up real well.



You could tell by the markings on the bondo what was fitting and what wasn't. When I had a good solid patch I test fitted it and it fit real well.






If you are going to use it for a buck do not add the sheet metal backing. So you can fill the bondo under the wire form. Also make sure you can get the wire form out. If it is going to be trapped make the wire form in to two pieces. Bolt it together so you can unbolt it so it will come out.

Hope this helped good luck with your project and don't forget to take pictures.

 

Well DAMN!

That buck worked great.

 

I have never tried it before and with the results, I am defiantly adding it to my bag of tricks.

It was a hard panel and I was scrambling to find a way to make it.

 

Brad do a test with the wax and see what you think first. Not sure what Ron uses as a release agent but everyone I know just use wax. Most of them use furniture wax.

If I was going to use it on a press I would use dura gl*** if it was me.

Let us know when the article comes out I would love to see it. If I lose track of this thread please send me a pm.

I will add you as a friend so I will be easy to find. I love reading tech articles.