A friend of mine approached me about a project to do some engraving into stone for a outdoor class room at a local grade school.  I had seen the technique at a stone carving conference in Lawrence Kansas.  After some research I was ready to tackle the project.  The stones were cut at a local quarry and delivered to me for the engraving/sandblasting.  I started by cutting templates on a COPAM vinyl cutter using a 60 deg blade and a sandblast resistant that is sticky backed.  I discovered right away that the stone needed to be free of any stone dust in order for the resist to adhere.  Once the resist was placed I was ready for sandblasting.

The blaster had to be filled several times and the job required about 4 bags of media.  The media used is Coal Slag.  Its a byproduct of the coal fired electric plants.  The greatest advantage to the coal slag over silica sand is that the coal slag has only .01 % silica as compared to sand being 100%.  Using a media with a low silica content  reduces the possibility of developing silicosis being developed in the lungs.  However using a respirator is still a must. 

I started out using Black Diamond but the grit was to course and kept getting clogged in the sandblasting valve.  I then found a similar product called Black Magic.  It was finer and didn’t get clogged in the spray nozzle.  Once the blaster was working properly the stone carving was rather easy.  The stone used in this project was called Silver-dale limestone.

        

Once the blasting was completed the letters were painted to create a stronger contrast.