A wee masking problem

how odd... I use Tamiya on all of my Alclad jobs with no problem.  Maybe you put the coat on a bit heavy?  I have heard futuring over the tape before painting also prevents bleedthrough and in this case, seep through.  Maybe that would be worth a shot... good luck and hope it works out for ya!

" Z " Heres what I have done and am doing now. Two methods with excellent results. On models I have completed the only thing that I had used up until now was Bare Metal Foil. Very thin so it conforms to all the raised lines on the canopies. Just dont burnish down too hard and use the point of a ' ROUND " toothpick to burnish it down around the frames. Use a new #11 Exacto blade and cut along the frame.Never had any leakage problems and ended up with a crisp clean line. If any residue is left just clean it off with a little Denatured Alchol or Floquil Plastic Prep on a cotton swab. The residue comes right off. I sometimes also polish the canopy first with a little Model Car Wax before applying the B M F. At present I am working on the Academy 1/72  B-29 'Enola Gay " and using Alclad II. Purchased the Cutting Edge " Black Magic " B-29 Canopy / Wheel Hub Masks. They are like a black plastic film, not as thin as B M F and each piece is cut to the exact shape of each window on the B-29. Just lift each piece off with the tip of a # 11 Blade. Cant make a mistake where each one goes. Since the nose glass of the 29 is rounded they seemed to NOT settle down real well. Whalla a way to fix that. Get your wifes hairdryer, set the heat to low, warm up the masks, the heat makes them more pliable and apply. They settle down just great and conform to the rounded surface. Have the fuselage already done with the ALCLAD and warmed up the mask, got a new # 11 blade, picked up one corner of the mask and gently lifted it off. Schazam ! A crisp clean line, no leakage, and no chipping of the Alclad around the frames. Hope this helps. It worked for me. Dennis