Problems with paint - changing properties

Difficult to see—always in motion is the…

When the gloss changes, it is usually a matter of pigment, although a change in the resin is a possibility, depending on the age of the paint. Some drying conditions can alter the behavior of some paints. For your situation, this problem is usually created by low temperatures, either on the painted surface or ambient conditions, or both.

How old is the original paint?

Was the paint ever exposed to freezing temperatures? This can cause exactly the symptoms you describe.

Second and most obvious, did you mix the paint thoroughly? This is often problematic with older paint that has been stored for awhile, whether on your shelf or on the shop rack. Try stiring the paint for about ten minutes with a flat metal stiring stick, making sure to put a strong vertical component in your stiring. See if you get the same results.

Third, did you mix anything with the paint in the original container? Even if it was the recommended thinner, changing the ratio of solvent to resin to pigment in a paint often changes the way the resin and pigment behave on drying. If you are using a recently cleaned brush, the solvent residue from the brush can produce this effect, especially in flat enamels.

Fourth, is there a possible surface contamination? How well cured were the underlying paints?

Triarius

    Original paint in both cases was less than a year old - paint was used in basement so temperatures were room temp or a little cooler.  Paint was thoroughly mixed with a paint stick until paint was consistant - no glob of paint at bottom of stick.  Nothing was mixed in the original container, just put my brush into the paint jar/tin.  I was painting over the original paint and the paint was well cured.

Tis a puzzlement????
jsfman

jsfman wrote:

Original paint in both cases was less than a year old - paint was used in basement so temperatures were room temp or a little cooler.  Paint was thoroughly mixed with a paint stick until paint was consistant - no glob of paint at bottom of stick.  Nothing was mixed in the original container, just put my brush into the paint jar/tin.  I was painting over the original paint and the paint was well cured. Tis a puzzlement????

'Tis, indeed. But you say the paint consistancy changed from the first to second time you opened the bottle? If thoroughly mixed, then something has changed rather drastically. This can happen, especially if the paint was old stock when you bought it.

Stiring paint until there is no "blob" on the end of the stick does not necessarily mean that you have complete dispersal of the pigment. I usually stir for a good five minutes after that if stiring by hand.

Still, I am beginning to suspect the paint may have gone off. If I think of anything else, I'll post it.