How to make a concrete bench

Step 4.8   Release the bench form

Slip a piece of board under the middle of the bench form.

Of course, you will need someone to tilt the bench back while you do that.

The board can be 1" (25mm) thick more or less, it doesn't really matter, and 20" (500mm) long x 6" (150mm) wide.

Stand on the two sides of the bench form and give a little bounce up and down.
This will break the seal between the concrete and the form. You will visibly see the seal breaking - a slight parting between the concrete and the form.
The seal will be more of a suction seal, rather than an adhesive seal, because of the release agent. Standing on the form and giving a little bounce will break that seal.

Now stand on the two ends (as opposed to the two sides) and do the same thing.

Now the concrete bench should easily lift out of the form.

If by any chance it does not, then turn the whole unit upright and knock one end of the bench form up by hitting it from underneath with a hammer.

You only need a little bit of air in to break any suction hold.

Mmmmmmm. Looks pretty good to me.