Some advice please. I have been using artists oils over a humbrol enamel undercoat as it seems tougher than an acrylic undercoat which tends to wear through when I apply and brush out the oil paint. For some reason blending the oils works better with an enamel undercoat. Have i got this all wrong? most figure painters seem to prefer an acrylic undercoat.

Paul

Paul,

I can only speak to what works for me.

I've never had any trouble with acrylic undercoats lifting when I put oils over them.

My process is to wash and dry the figure with detergent and water before I prime.

I use Tamiya XF-2 Flat White for a primer, applied by airbrush. To reduce the paint for airbrushing, I use a 1:1 thinner mixed from lacquer thinner and Tamiya's X-20A thinner. I use this mixture to reduce the Tamiya paint at about 7:3 or 3:1 paint to thinner.

Priming the raw plastic or resin will help significantly with adhesion and durability of later paints, especially the water based acrylics. I like to use white because it lets me see the later colors in their pure tones. I like the Tamiya paint because it's a solvent based (not water based) acrylic and the solvents chemically bind the acrylics together and to the surface. The Tamiya paint also dries "tight" and thin and does not obscure details (unlike some heavier, sanding primers).

For acrylic undercoats, I use, variously, Vallejo Model Colors, Citadel / Games Workshop, Andres, or Reaper paints. These are all water based acrylics. I apply these by brushing.

To thin these acrylic paints for brushing, I use a mixture of Vallejo Model Color Thinner (which is actually an acrylic medium) and water. I mix this 1:1. After mixing, I add in about 5% each, by volume, Vallejo Matt Medium, an artist acrylic flow enhancer (Grumbacher), and an artist acrylic drying retarder (Golden).

(I have used both Grumbacher and Golden brand artist acrylic products with equal results. Vallejo actually makes an entire line of artist products, as well. I don't think brand is particularly important here.)

To thin the acrylic colors for brush painting, I reduce them about 1:1 with the above mixture. This produces a very thin paint mix which has to be applied in 2-3 coats to achieve good coverage. However, it will not obscure details or show brush marks if allowed to dry between coats.

Properly thinning acrylic paints is important to getting smooth applications and also for durability. If you only thin these with water, you will dilute the acrylic binders too much and they will not be strong enough to hold the paints after drying (especially to raw plastic, resin, or bare metal). Adding back these binders by using an acrylic thinning medium is the solution, especially if the paints are to be thinned enough to brush well and not build up, hiding details or showing brush marks.

I apply my oil paints more or less straight from the tube without any thinning. When I do need to thin, make a wash, or for brush cleaning, I use ordinary mineral spirits - not turpentine. Turpentine (all brands that I have tried) can be very aggressive with underlying paint layers as well as imparting unpredictable brushing characteristics to the oil paints thinned with them.

Once I've washed my figures for priming, I try to never touch it again with my hands. I mount the figures on pins and use hemostats to hold the figure by the pin for painting. Oils from your skin (natural or transferred from other objects) can adversely affect paint adhesion. Of course, this also avoids finger prints or rubbing the paint off the figure.

HTH,