Mei-klaf and spray-klaf
I talked to someone who makes this kind of stuff. He said that in the past mei-klaf were made from contact cement dissolved in a volatile solvent. The contact cement caused yellow stains on the klaf. Now, mei-klaf and spray-klaf are made by dissolving various types of rubber cement in a highly volatile solvent. Anyone who ever used rubber cement knows that it is one of the worst possible adhesives around. Anything that sticks to dry rubber cement falls off after a while. Water-based ink is not compatible with rubber cement. That's why there are so many cases of the ink easily rubbing off. A member of the אור לסופר forum wrote: אחד המתקנים (מביאים לו ס"ת אחרי הגהת מחשב) בירושלים אמר לי שהוא מיד יודע אם השתמשו במי קלף או לא לפי קלות המחיקה The use of mei-klaf makes it much easier to erase the ink, which means that it reduces the adhesion strength of the ink to the klaf, which leads to early פסולים in the STAM. We want to improve the adhesion of the ink to the klaf,