I've seen this kind of blistering happen before but not had to deal with prepping it. Sometimes there's a lot of resin in the wood that comes to the surface, the best way to get rid of resin is an IR stripper. It might not be the problem but if it is it might be possible to seal it with 'knotting', basically shellac.
I've seen this kind of blistering happen before but not had to deal with prepping it. Sometimes there's a lot of resin in the wood that comes to the surface, the best way to get rid of resin is an IR stripper. It might not be the problem but if it is it might be possible to seal it with 'knotting', basically shellac.