OT question

[monte55]

I am making a mold on my CNC router table in MDF. The image will be reversed
so when I put in the concrete the positive will show when released from the
mold. I am sealing the MDF with spar varnish. My question is.......what can I use as a release agent so the concrete will separate from the mold smoothly. Grease, Pam, silicone spray,WD 40 or whatever? I imagine I'll have to separate them while the mix is still green but set. Any ideas?
These will be used for personalized stepping stones and such.

Thanks

[50bmgshooter]

I use used motor oil on foundation forms
also on smaller items I have used liquid soap

[aametalmaster]

When i worked in the bath tub factory we used silcone for mold release. Sprayed it on with a spraygun kinda heavy...Bob

[6010]

Having not tried this, and this is just a hunch, MDF is very smooth and I don't think there will be a problem with separating from the concrete. Unless someone knows for sure, if it were me I would make a little trial run before I started on the actual project. I have noticed better results when I tear down the forms on a concrete job when the concrete is a little green - like next day or so. You don't have to seal the MDF - it is a lot tougher than that.

I just finished a house I built for my mother in law about 3 months ago. I did all the work from digging and pouring the footing, laying the steel, the masonry, framing, roofing, plumbing and electrical. The only thing I did not do was the sheet rock and the insulation. Most of the work I did with only one helper and a lot of the time I was working by myself. Except for the roof. the two of us did all the work.

I really liked the MDF board. I got about 40 pieces as a going away present when I left the paper mill. I had never used it before and didn't know how easy it would be to work with. I made all the molding - baseboard, window, door and made the vanity out of MDF. I was amazed at how easily the MDF milled down with the router.

Now I know this is off the subject - way off. But I wanted to brag a little and let you guys know what a real Black and Decker project is like

Please don't beat on me too hard

[jjsjeff]

Most of the time I believe these concrete stamps are made out of rubber. I know the company I did a project at (I'm a PLC programmer) sold the stamps and they were made out of thick rubber.

As far as something that won't stick? I'd almost coat the MDF (epoxy maybe) since it likes to absorb water and then use something like silicone. You could probably use about anything that you don't mind being on the concrete after you press the cement.

[monte55]

Thanks for the replies guys.............I know MDF will swell up like a BALL Park Frank when it gets wet. The mold has to be used multiple times.

[Archaic]

Monte:

You need some Form Release Agent. Used to be called Form Oil, or Form Release Oil back in the old days. There are two different formulations now. One is oil based and the other, more environmentally friendly, is water based. It was developed back in the day when almost all concrete forms were plywood, which is real "grabby" where concrete is concerned. Put it in a pack sprayer, spray your form really well, and you will get easy strip and multiple uses. I buy the stuff in fifty-five gallon drums but I am sure that you can get it in five gallon or smaller quantities. Call your local Ready-Mix concrete plant and ask them for a name of a local business that sells concrete accessories to contractors. Tell them you need some form oil, or form release oil. Stuff is relative cheap, non toxic, and easy to use. For me the oil based has always worked better than the water based.

Adios-----

[monte55]

Maybe I should have stated the forms are small..............say 18" square.
This is not a high production form......

[calweld]

Around here, all the concrete guys use diesel . . . just put it in a regular pump sprayer . . . spray the forms just before pouring.

[monte55]

Hey Cal...........how about kerosene?