Another Primer Question

Here's the definitive answer:

It depends.

Hopefully, the worst you'll get is just some really long drying time for your base coat; however, depending on what and how you put it on, you could get everything from non-adherence of your basecoat, to lifting of the primer from the substrate. And if you put an enamel over a wet acrylic, you could end up with a real mess.
Best thing is to let ANY paint cure fully (I'm not talking about auto top coats) before applying the next coat--particularly if you're dealing with varying paint types: lacquers, acrylics, enamels, etc.

Just my opinion. Hope this helps some.
Gip Winecoff

The primer will take a lot longer to fully cure. As paint cures it gases are released. In some cases this can cause bubbles in the base coat. Additionally, since the primer is not fully cured it can cause it to be pulled up by masking tape. Third, and this is not normally a problem with acrylics, but spraying enamel or laquer over non-cured enamel can (in extreme circumstances) cause it to dissolve.

Edit ... Gip and I must have been writing at the same time

Thanks for the replies. I haven't done it yet, I was just curious. On a related note, is there a rule of thumb for the amount it takes to cure enamel primer? I'm under the impression it's three days minimum.

Once again, it all depends. Spraying with a rattle can will usually take longer than paint applied with an airbrush, because the former is thicker than the latter. The number of coats applied will cause a difference, as will temperature and humidity.

I am an enamels person, and once the piece is primed (airbrush), I can usually spray my topcoat the next day. Personally, I like to give primers a good 24 hours to dry. I'll give my topcoats about 48 hours or so to dry prior to washing--maybe even a little longer.

Figure longer times with heavier and/or multiple coats.

Gip Winecoff

Thanks for all the help.