Has anyone used gesso as a primer?

[Helper Monkey]

I have a bunch of gesso in my art supplies. I was thinking I could thin it down with Tamiya Thinner, add GAC-200 to promote adhesion to plastic and maybe add a little black to turn it grey. Has anyone ever done this?

I have used the AK interactive but I didn't really care for it much. I know gesso is sand-able because I sand between coats when I prime my canvas. 

[Mike Kucaba]

You can use whatever you want to primer...that don't necessarily mean the results you'll get is what you want. I use automotive primer in quart cans and this is so thick that I thin it 2: 1 and more. 

I think you have more experience using gesso so give it a try. Test on some junker bodies or the plastic spoons

[Exotics_Builder]

I would sincerely doubt it would work with Automotive paints that are enamel or lacquer.  It would likely work with acrylics, but I would suggest alternatives.  The only use in automotive modeling I ever came across for gesso was in some detailing, where artist oils were used and for painting lettering on tires.

[Ace-Garageguy]

I did try acrylic gesso for whitewalls on vinyl tires (that inhibit drying of lacquer and enamel paints), and it worked.

I'd think gesso, on plastic, might shrivel and alligator if topcoated with lacquer or enamel though.

On the other hand, I HAVE used acrylic-urethane clear for cars as a final glosscoat over some of my paintings done with acrylic artists colors, and it worked beautifully.

As suggested above, experiment.

[Helper Monkey]

I ended up mixing 4 parts white gesso (from Daniel Smith), 1 part Carbon Black Golden High Flow acrylic, 1 part Golden GAC-200 and 2 parts Tamiya X-20A Thinner. I did a test spray on a hood that I washed and sanded with 1600 grit sand paper before hand.

The modified Gesso went on really well. I only sprayed a thin layer in order to test it. It sanded well with the 1600 girt paper, but it went down to the plastic really fast. Most likely due to the fact I sprayed such a thin coat. I did not get any flaking, chipping or anything like that however.

It did bring out the light scratches on the underside of the hood. I am debating if I am going to resand the entire underside or if I am going to brush on some gesso there and see how it fills scratches..  I waited about a day before I sanded. Since it is acrylic it does have a tendency to shrink and I wanted it to cure before I attempted to sand it. 

Over all I am impressed. It worked much better than the AK Interactive stuff I tried. I am going to experiment and see how it goes.