Bluestone is a very porous stone and engraves quickly so you don't need a lot of pressure or passes to achieve a suitable paver depth. Regardless of what type of mask you use there may be an adhesive stain left of the paver from the heat and pressure of the blast. This can be cleaned up with warm soapy water and scrubbing brush or a domestic pressure washer.
We recommend 6mil or 9mil PhotoMask but you can use 5mil as the video will show. Obviously you can use vinyl mask as well which will allow a deeper etching but in this video we will just focus on PhotoMask that achieves about 0.5mm depth which is ideal for donor paver engraving or any paver that is going to be walked over. You can also use LaserMask to create stencils.
Oh by the way, we sped up the video during blasting. The actual blast time to achieve 0.5mm depth over the area of about 30cm x 20cm was 5min.