Bending Wood / MDF

“Where the curve starts a proper earning ends” my grandfather, a carpenter by trade, used to say.

Well, after some experience gained I totally agree with him. Compared to angular joints curvy and bendy shapes made of wood take an infinite time longer to make. The best way to bend wood and medium-density fibreboard is by the use of steam. Since I don’t have a steam chamber I was looking for an easier way for an aspiring project, the make of a flowerbed for my balcony.

This Instructable shows a technique almost forgotten – shaping wood and medium-density fibreboard by watering it and the use of ammonia.

Those are the things you need:

• several clamps
• Ammonia (I used a 10% solution)
• spray can
• tension belt
• wood glue

PLEASE NOTE: ammonia solution, or ammonium hydroxide, to be precisely, is an extremely hazardous liquid. It was widely used as a household cleaner until a couple of decades ago. The stench is almost unbearable.

Always wear goggles, gloves and a mask and apply it only on the outside!

The principal idea is to bend small layers of wood and / or fibreboard, let them dry and then glue them together.

First I sprayed the cut pieces with a 10% ammonia solution on both sides. I did this twice and let everything dry for a day.

Then I watered the pieces. The strong stench of the ammonia is nearly gone, I did this in my shower cabinet.

After the soaking I bent the pieces around the shape they should take and fixed everything with clamps.

I left it that way for a couple of hours, then took it off and fixed it by the use of a tension belt. This is for letting the material dry off, also for keeping the shape (it would otherwise go back to almost normal).

A day later you can start glueing everything together. Take wood glue and coat the entire contact area. Again put it around the shape or a pattern and press it as strong as possible together. Let it rest for 24h and take it off.

Sometimes some smaller spots on the edge between the layers didn’t properly stick together. I inserted wood glue into the gaps and pressed it again with a clamp.

I made the bent part of the flowerbed out of two layers of MDF, about 8 mm thick, and a thin layer of wood with a thickness of about 2 mm. The latter was for the visible surface, it shall match with the other parts of the construction.

IMPORTANT: Since it is almost impossible to measure the proper length of a curve before, make sure all the pieces are a bit oversized and do the cutting later in place.