Jerk it off with a snapping action. If the tape is free of paint,the new paint is well bonded to the old surface. If the new paint adheres to the tape, the old surface is too chalky and needs more cleaning or the use of an oil-based primer. Cross-grain cracking occurs when paint coatings become too thick. This problem often occurs on older homes that have been painted several times.
Paint usually cracks in the direction it was brushed onto the wood.
Once cross-grain cracking has occurred the only solution is to completely remove the old paint and apply a new finishing system. To prevent cross-grain cracking, follow the paint manufacturer's recommendations for spreading rates. Do not repaint unweathered, protected areas such as porch ceilings and roof overhangs as often as the rest of the house. If possible, repaint these areas only as they weather and require new paint. However, if repainting is required, be sure to scrub the areas with a sponge or bristle brush and detergent in water to remove any water-soluble materials that will interfere with adhesion of the new paint.