Can I use hairspray in sealing? Or can I just not seal it?
The only thing hair spray does to the blade is protect it from splintering when I change the rubber. It is like sealer, but it has no effect whatsoever on how the blade plays. You have to be really careful with a lot of sealers because they can make the top surface of the blade harder, especially if you use too much. That changes the way it plays. This is an especially big problem with polyurethane sealers and other things like it. Note, sealers don't make the blade softer, they make it harder*. SOmetimes very much so, and usually right away. Especially with expensive soft blades like a Viscaria, you don't want that to happen, but you still want to protect teh blade from the glue. So when I change rubber (or the first time I glue rubber on a new blade) I spray the blade one or two coats of old fashioned hair spray and let it dry for an hour. Then I glue on the rubber sheets. It makes it so that when you remove the sheet, you don't take any wooden pieces with it.
* some sealers penetrate fairly deep also, so if you mess up with it, you may not be able to restore the original playing properties by sanding the surface. This is not true with all, but definitely a problem with polyurethane, which is designed to penetrate into the wood. Again, this is not a problem with hairspray.