[Woodco]

Pics, and what products are you using, and how are you applying them?

 

[Woodco]

Can you tell if the bubbles are coming from underneath the primer, or in between the paint and primer?

 

[Woodco]

Everyone here claims you need to use oil based primers outside. Stix is formulated for glossy hard to stick to surfaces. Wood is porous, so its kind of a different category. It could be that gases in the wood pores expanded in the heat... Maybe you didnt let the primer dry long enough before topcoating... The best thing for exterior wood is something that penetrates , which isnt really what STIX is designed for. Not saying its not good for wood, but in your situation, a penetrationg primer like an oil base would get in the pores deeper, and you'll have LESS of a chance of that happening.