Home-made gesso

[GregShelton]

Hi everyone,

I recently went on an excursion into the world of papier-mache after having discovered that it has been used to make boxes and even furniture in the past. I have played about with the material and I have been pretty astounded by the results (much better than you might think for it's all its primary school art class reputation!). The one thing I found out was that the most important part of creating a project with smooth professional finish was the application of a finishing, sealer coat of gesso.
I didn't even know what gesso was, so I had a look online and straightaway I was directed to homemade alternatives. I tried a few recipes but the one that has worked the best, producing a strong and solid coat with great adhesion and sanding properties, is this (I forget the quantities) : PVA glue, acrylic paint, talcum powder and water.
After having read a little on finishing, I saw that gesso can be applied to wood so I tried and was very happy with the results when I used it to seal a piece of MDF for lacquering with an alkyd urethane-based black lacquer varnish.
There don't seem to be any problems with adhesion at the moment but are there any pitfalls to this gesso recipe? Will it crack, fall off or interfere with the lacquer layer in some way later down the line? Will I get dots or bubbles of some sort due to the composition of the talc, paint or glue?

Thank you!

 

[ED65]

There don't seem to be any problems with adhesion at the moment but are there any pitfalls to this gesso recipe?

I wouldn't expect adhesion issues with the recipe you used as it has abundant binder. Ignoring the water PVA is basically all binder, and acrylic paints are very heavy in binder.

The talc is basically there to aid sanding (same reason it's added to epoxy fillers).

There is one potential technical issue as regards making up this sort of thing, when adding a dry powder into existing liquid "emulsions" it is very difficult to get the powder fully wetted, all clumps (referred to technically as agglomerates) broken down and even distributed through the liquid (dispersion) if you are simply adding dry powder to some/all of the liquids and then mixing, even if power mixing. Did the source of the recipe you followed talk about this at all and the method accounts for this?

Will it crack, fall off or interfere with the lacquer layer in some way later down the line?

Well gesso was used extensively on wood and despite not being noted for flexibility it could still last in good condition for centuries. PVA and the binders in any common acrylic paint are plenty flexible so I think you should be fine as far as cracks go if there's no too much talc incorporated and it's dispersed well.

I don't know how many substitute gesso recipes you found but there are nearly as many versions as there are opinions on what a substitute should be like :lol: And even the real thing, gesso sottile, has innumerable minor and major variations depending on where and when it was made. The main point is, as it always has been, to get a primer that you can work with and that does what you want and you seem to have that.

One thing you may want to look at though is whether this recipe has enough 'tooth'. Uralkyd-based enamel should bond very well, but if you're concerned about long-term stability you should do some tests to make sure.

 

[sammy.se]

My other hobby is art, and i use gesso (white and black) a lot to prime and re-prime my canvas.

Thing i love about gesso is the high quantity of pigment - two coats is enough usually to cover whatever is below (black gesso, one coat can cover white).

I try and avoid PVA because acrylic (especially thinned down) won't stick very well. In a pinch, I've used PVA to prime wood or cardboard before oil painting.

The only problem I can forsee with PVA is if you need to sand down / de-nib and apply water based paint...

Is there a reason (besides cost) that you wont use ready made gesso?



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