Some other potential solutions ($0.02 worth):

• Silicone (from Armor-all and various lubes & cleaners) can cause pinholes (actually, fisheyes in this case). Surfaces must be thoroughly cleaned and prepped.
• Try routing some hard lines off your air compressor that go up to the ceiling, across the ceiling a bit, then back down. This line should also have several drops for catching water. A Google search will get you to some plans with adequate dimensions, details. I can find it if you don't have any luck.
• Is the air compressor cold? You may want to relocate it to a warm place (heated basement, for example) and plumb hard lines to your paint area.
• Are the fillers and primers given adequate time to cure?

A good air dryer is a must, of course. I have a cheap air dryer and it is next to useless.

 

it could be solvent "pop" from using the wrong temp reducer/activator. the temperature of the metal you are spraying could be much cooler than the air temp. that causes the paint to solidify on the outside trapping solvent which then pops through. i got a non contact thermometer from harbor freight to check the metal temp before spraying. i also have a a motor guard filter/dryer that turns pink when its saturated at the gun as well as an air guardian drier on the line that goes to the gun from the regulator/filter. last winter/spring i painted a triumph t100c tank and side covers about 8 times before i figured the out the air vs metal temperature and moisture in the line issues.
hope this helps

 

Solvent Pop

This problem is definitely solvent pop.

Solvent pop is defined as "Blisters, pinholes, or groups of pinholes on the surface caused by trapped solvents in the material - a situation which is further aggravated by force drying or uneven heating."



This can apply to bodyfiller, primer, paint, or clear. The most common causes are:

Improper surface cleaning or preparation

Wrong thinner, reducer or Basemaker.

The use of fast-dry solvents, especially when the material is sprayed too dry or at excessive pressure, can cause solvent popping by trapping air in the film.

Thinner too cheap.

Excessive film thickness.

Too low or too high air pressure.

Painting in too high of a temperature for the product being used or with the wrong thinner.



Prevention:

Thoroughly clean all areas to be painted

Select the thinner, reducer or Basemaker that is suitable for exsisting shop conditions

Do not "pile on" undercoats and topcoats. Allow sufficient flash time between coats and proper drying time.



Solution/How to fix:

If damage is extensive and severe, paint must be removed down to undercoat or metal, depending on depth of pops; then refinish. In less severe cases, sand out, resurface and retopcoat.

 

I'll try to reply to the comments as best I can: I do add anti-fisheye to all paint, but also am quite fanatical regarding cleanliness. An example is I use a prep solvent before starting any sanding on the body, even if the car has sat for 20 or so years.

I do worry about temperatures, but I'm pretty much at the mercy of Ma Nature. If painting in the summer, I start painting around midnight. Since I'm in So. Cal. the temperature extremes aren't as extreme as in more northern climates. I don't use any force drying. And yes, I use the same brand of reducers as the paint - which is single stage DuPont Chroma One urethane.

I'm also concerned I might use overly high air pressure, so will try dialing it down a bit. I use a Sata Jet RP and just purchased a Sata KLC RP for primer.

Bill77, is your air dryer less expensive/quality than the Harbor Freight unit? I only paint about one car a year, so I have to think hard before spending a lot on equipment.

I've often wondered about flash time in that if I do it too soon or a bit too late.

I've never had to repaint because of pinholes, but use a 00 paint brush and touch up all of the pinholes after doing the initial 1200 wet sanding.

My paint jobs turn out quite good, but I'd sure like to avoid the incredible amount of time required to spot and then make sure every pinhole has been thoroughly sanded down flush.

 

Sorry, I should have been more specific. I have this cheap canister:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=1118

which they claim will dry the air "to end paint failures". It didn't seem to reduce the condensation in the air supply at all.

 

?

Is it possible for you to post a picture of the problem? Everyone's comments were great but perhaps we can prescribe the proper remedy if we see a picture of these 'pinholes'

 

i found the following in my reseach notes when i was having the pinhole/crater problems last year. i got it from one of the online autobody/ paint forums. it may help with the evaluation of your problem.
"Fine dust particles that fall on a tacky surface can be encapsulated by the finish, creating an appearance almost identical to solvent pop. This "solvent pop" appearance usually occurs on vehicles that are removed from the booth in a tacky condition and placed in another location to dry. Fine dust contamination can be removed by sanding and polishing. However, If the condition is solvent pop the finish will contain pinholes or small craters after sanding."

bill