Funny White Spots

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Posted by Catharine C. Kennedy on July 12, 2002

I am just new to sign painting (being a sign carver, this is a logical extention). I am working on a sign on overlaid plywood, primed with Cooke's primer and painted with latex paint. When I put the one-shot color down, funny white spots appeared. These are covered by a second coat of paint. I've used one-shot colors for a while now, and this is the first problem (opportunity) I've had. What am I doing wrong- or better yet- what should I be doing?!
Thanks

Barbara Schilling

Are the white spots on TOP of the one-shot, or are they "holidays" where the paint crawled away from the surface?

Catharine C. Kennedy

The background is white so perhaps the paint has pulled away. (?)

Barbara Schilling

Perhaps Kent Smith will see this post and jump in. He could probably address the possible chemical reactions more scientifically.

I think it sounds like the paint is "crawling". The latex vs. oil base is probably the culprit. Sometimes this crawling is referred to as 'fish eye' or 'holidays' (because the paint took a holiday at that spot.) You could try a couple of drops of fish eye eliminator (from automotive paint supply store) in your lettering enamel. Also, make sure to thoroughly clean the oil out of your brushes prior to lettering. That can also make problems. And once your lettering paint is contaminated it gets hard to correct, so always paint from a cup, not the can of paint. If your background was oil based enamel I would suggest wiping it down with Chromatic Hi Temp reducer. Since it is latex, you might need to give it an alchohol wipe. This MAY give the surface a slight temporary 'tooth'.

These are the things I would try first. We have actually gotten away from latex backgrounds and gone back to Bulletin enamel. We have had more predictable and successful results. All the signs I did during our "switching to latex" phase have not performed well. I think my customers stay in business too long. I will opt for better quality and deal with the environmental issues as best I can.

Catharine C. Kennedy

Thanks for your prompt reply- certainly give me another area of which to be aware! Learning curve!

Kent Smith

Unlike some other primers, Cooks has a vinyl water proofing additive. For the most part the acrylic in the primer allows enamels to adhere to it just fine. When there are smooth, hard spots on the surface or when the primer has not been thoroughly stirred, there can be spots of almost pure vinyl resin laid down and the enamel will not adhere to these spots. This phenomenon can also happen when the ambient temperature is above 75 degrees.

Barbara Schilling

Kent,
Catherine said she used Cooks primer and THEN latex before lettering with One Shot. Could the vinyl resin be migrating through the LATEX background?

Kent Smith

Typically an acrylic will stop vinyl migration but latex will not so there is a possibility of migration.

Mike Jackson - Or maybe something in the air

Just to throw out the possibility that some white spots or "fish eyes" can be caused by something in the air such as WD-40, spray fixative, hair spray, or any similar product.

Mike Jackson