Thinner turned paint int "jelly"

Tools, Techniques, and Reference Materials Painting and airbrushing
1

I’m a fan of Polly S acrylics and subsequently use the Polly S thinner for airbrushing :). Anyway to cut a long story short we had a baby and the modelling got shelved for about a year.

Last weekend I pulled out my stored paints and 2/3 full year old thinner and started to paint a base for one of my planes, Upon mixing the old paints with the old thinner, the paint turned to a goey jelly like substance which was a nightmare to clean out the airbrush. Thinking the paint was the problem I purchased a new bottle of paint and mixed in the old thinner and Kazaam! - jelly ! After spending another hour cleaning the airbrush I bought new thinner and new paint but after spending a long time cleaning my A4777 airbrush I’m worried that I’ve forgotten something in my year long hiatus. Any ideas as to whats going on ??

2

How was the paint and thinner stored? If the temperature is too hot or too cold it could cause damage to the thinner and paint. I use enamels and have thinner that is about a year old and haven’t had any problems. However, I do have noticed that some paint does get gooey after it has been opened and I don’t use it for a month or so. To sum it all up, keep your paint supplies fresh and be careful with older paint.