Concrete – Do I need any kind of separator / release agent when casting concrete in shuttering plywood forms

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We'll be casting my first concrete countertops soon. We already talked thickness, reinforcement and sealing with manufacturer of concrete mix we will be using (great guys!) so on that part, we feel safe.

As you can see below, plywood has really smooth finish. I'll seal and round edges with silicone. My question is – do I need to spray form with anything? Or can I just clean it and pour concrete? It looks like it is designed to not need any separating agent, but I prefer to ask before I pour.

We'll be using extra smooth mix designed for countertops and small architectural details, if that matters, and designed thickness is 3cm /(1 3/16 inch).

Photo of smooth finish

Best Answer

I've seen this done with melamine-coated boards. I would make sure that the plastic veneer of the boards you're using is one solid piece. Family Handyman indicates you don't need any special chemicals to get it out of the form

To remove the form, pry off the long sides and then the short sides. Pry against the form base rather than the concrete. If you have to pry off the form base, use a plastic putty knife; metal will mar the surface

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