Joe, I have been using Mas slow for the last two boats. I like it, but it did exactly that to me on an interior fill coat. It was well within over coating times and the previous coat was still rubbery, but not tacky. I did not feel that it was blush, just that the low viscosity resin is more prone to the effects of surface tension, especially on a smooth surface.

I adjusted my approach to over coating since to get fill coats on while the previous coat is still quite tacky, It has worked perfectly for me. The previous coat did not become more fluid, but the top coat also stayed put.

For the last boat I was over coating four hours after finishing the previous coat at 65 to 68 degrees.

This actually suits me very well, as I no longer have to get up at three in the am for a fill coat. If I start early I can get all coats on by bed time.

If you are presealing the hull you don't want to add cloth too soon or it becomes a sticky nightmare to try to adjust, but the weave of the cloth should break up the surface tension in the wet out coat.

I do wet out on unsealed wood, so that is just an assumption.

Et

The picture is Mas after two fill coats over 4 ounce. No voids.