Testors decal sealer. Comes in an aerosol. You spray it on the decal sheet BEFORE you 'install' them. Seems to do a fine job of locking the graphics, while retaining all of the flexibility of the decal so you get good surface adhesion.Two or possibly 3 VERY LIGHT coats are much, much better than one heavier one.....you definitely do NOT want the stuff to 'run' off the sheet while drying. I do this on all 'home-made sheets. The commercial ones are already done for you.....PLATO being the exception.