Paint tests, part 1

Late last year I discussed painting leather and promised to do some testing to see if oils or gouaches weathered better. The implication was that the originals could have been done with either, again mainly me trying to justify not waiting a week for each coat of paint to dry.

I’ve just started painting and  have my answer already.

I’ll briefly recap first. Six samples of the same 4mm harness butt were stamped and dyed, three with a modern water based black dye and the other three with a home made iron-based dye. One modern and one traditional sample were then painted with each of oil paint, gouache and acrylic. The stamped area was used to see if there’s a difference between compressed areas and paint on top of the leather. The number “1” was used as it had a  number of sharp points where failure could occur.

Paint tests

The samples and paints. The gum arabic is for diluting the gouache, the gum turpentine (out of frame) for the oil.

The gouache flowed beautifully on the modern dye, as did the oil on both samples. The acrylics had a really hard time covering the black base on both samples. The acrylic will need a minimum of two, and possibly three coats to cover as well as the others. The problem with both the water based paints is that the iron dye makes the leather hydrophobic. The water-based paints bead on this surface, leading to rough edges and poor adhesion.

Paint tests

First coat finished, I’ll tidy the edges on the next coat. From the top down are acrylic, gouache and oil, the iron dye is on the left. The beading can clearly be seen on the 1 in the centre left sample.

The moral of the story is that if you are using an iron dye, you have to use oil based paints.