Just repainted my old home (1923) – lap siding – used Behr paint w/primer included — scraped off all old paint. Now bubbles and blisters have formed. What caused that and how can I prevent it from happening more and more?
Well most likely you power washed the siding, right. If you did then Most likely there was still moister in the siding from power washing when you painted. If you didn't power wash then there was dirt and dust left on the siding. Both of these would cause the paint not to cure to the siding.
Last but not least is that it could be the paint. Behr paint is known for having major issues. The first time I used Behr I had to go over the house 3 times before I got coverage and even then it barely covered. The second time I used it I could not get it to bond or cure to the siding similar to this situation. I should not that the owners supplied the paint, I use Columbia, Sherwin Williams, or Benjamin Moore, and Kilz origanal primer(oil Based).
There really is nothing you can do to prevent more bubbling and blisters from accruing, the only thing you can do is as you see them scrape them till they stop peeling, then wipe down with TSP, it is a detergent that leaves no residue and will remove all dirt, dust, hell it will even remove nicotine stains. It can be found at most hardware stores. Then re-prime and paint the area.