How to prime an mdf board with gesso

The term "gesso" can be something of a misnomer, as some people use this word to describe acrylic primer, which is completely different and doesn't work with egg tempera paints. Gesso for egg tempera or ET can either be bought ready-made (ask at your local art shop) or you can mix your own recipe.

For this project I used ready-made gesso and a recipe for gesso, which a friend told me about. I then compared the two to see which provided the best surface.

You will need to make a suitable surface as ET needs a rigid support. I have used mdf board in the past to paint on with acrylics and it provides an excellent surface as it does not warp. Avoid using green mdf as this has been treated to be water resistant, so may effect any paint used on top. I decided to prime several boards at once and save them for future projects.

Ready-made gesso is fairly expensive (for a small pot I paid £7.95 for 30ml from Green and Stone, London), but it saves a lot of mixing beforehand, although it is still time consuming to apply. A small pot was enough to apply several coats to two A5-size mdf panels.

One: It says on the instructions: "Heat using a Bain Marie". I don't have one of those so improvised with an old tin and a pan of water. I heated the gesso within the tin to avoid direct heat.

Two: When heated the gesso becomes more liquid and is easier to brush onto the mdf panels. As soon as one layer becomes cold, you can add the next layer.

Three: Add as many layers as is necessary. Leave the panels to dry for 24 hours and then the gesso should be ready to smooth using a fine sand paper.

This recipe provides a much cheaper alternative to ready-made gesso and is also fun to make too. The ingredients are fairly cheap and easy to come by and seems to do the job. It's a good alternative for those wanting to try using egg tempera, but want an easy and inexpensive way to start.

One: Add 3 parts water to 2 parts white (PVA) glue. The amounts are not exact, but it shouldn't be too watery.

Two: Add the talcolm powder until the mixture resembles batter. I added too much to begin with, so added more water and glue.

Three: You can speed up the drying process with a hair dryer, although it is probably best to leave overnight before sanding.

Four: The ready-made gesso seemed to have a harder surface so I used coarse sandpaper to begin with and then a fine sandpaper to finish. The gesso recipe seemed more powdery and was easier to sand.

Verdict: The ready-made gesso provided a very smooth surface when finished, although the gesso recipe works well too.

Pros: The ready-made gesso will give you the most traditional base for ET and is probably the safest to use. The alternative recipe worked well and is a much cheaper alternative.

Cons: The ready-made gesso is expensive to use and not a viable option for regular use. I posted the alternative recipe on a egg tempera forum and the feedback was:

"You're not technically making a gesso if you're using acrylic polymer. It's a form of primer, but not the best for ET. The polymer is only working because of the porous nature of the talc, which isn't the best choice either except maybe for gilding."

(thanks to David Clemons, Egg Tempera Society)