Using a CNC Router to Create Masks for Sandblasting Stained Glass
Monogram Sun-Catcher (2015)
Why I chose to develop this method
There are other methods to etch stained glass, but these did not seem the best way for me.
Traditionally it is done
using an adhesive mask which you adhere to the glass then cut out your pattern in the mask with a knife and then sandblast.
For me this had several issues.
There is a fair amount of time required to cut out the mask.
This may be fine for one-off work but did not seem like a good way for repetitive work (I made about 20 versions of a basic design).
The mask did not appear to be reusable.
My design had a fair amount of repetition and I wanted to reuse the masks multiple times.
I have seen methods using a spring loaded cutter or grinder in a CNC machine.
My CNC has no provisions for cooling.
I was worried about possible damage to my CNC from the glass dust.
I tried various speeds and feeds with wood bits
I had limited success
I claim there was residual stress left in the glass
I was worried about possible damage to my CNC from the glass dust.
An overview of the process
Design the pattern
Use a CNC to cut the mask out of foam sheet
Glue foam mask to the glass
Sandblast the glass
Remove the foam mask for reuse
Details of the process
1. Design the pattern
I use Vectric software and while the learning process is fun, it is too big of a subject to cover in this document.
Vectric has excellent tutorials and forums.
Consider putting alignment features into your pattern showing where the pattern belongs on the glass
I added small holes at the corners to help align the pattern to the glass on the larger pieces
On the smaller pieces I cut the mask outline to match the outline of the glass
Do not forget to allow for foil and a bit of glass border around the outside of your pattern
I used layout lines 1/8 inch in with 7/32" copper foil
Mask islands such as the middle of the letter R will need special handling
I used a profile cut with the depth set to bottom of foam - .010" with a slow feed rate and medium speed.
There is a small tendency of the foam to defect rather than be cut, the following helped:
Glued down the foam sheet to a MDF waste board (was handy cheap and worked),
Wheat paste, cheap and water soluble
Reduce very sharp radii
Resort to only cutting some portions part way through
Used tabs for this but other methods could be used.
Foam Sheet
Stencil Cut
Cut Stencil Excess Removed
Stencil Closeup
3.Glue foam mask to the glass
I used wheat paste it is cheap and water soluble
Mix flour and Water
Use plenty of water
Viscosity about half of light machine oil
Mix until few or no lumps
I claim mixing with too little water early on contributes to lumps in the paste
I claim mixing with warm water early contributes to lumps in the paste
Coat both sides
Press firmly but watch out for distortion of the mask
On the bigger pieces I also used a J roller
I already owned.
Wait for the glue to dry before sandblasting (8 -24 hours)
Adhering sand or air pressure lifting the mask are sure signs of impatience
Large areas without cutouts take longer to dry
Monogram Stencil Glued to Glass
4.Sandblast the glass
I was unable to find tips for my old sandblaster at less cost than this new sandblaster. So I used this Campbell Hausfeld AT1226 Sandblasting Kit
less than $20 plus shipping still cheaper than replacement nozzle for old blaster
I found these tips
for less than $2 each and they do fit properly. I eroded two doing 20 sun catchers and many prototypes
I now have 8 spares
I used full pressure or less as the tank drained
I live in Florida so i simply used sand from my yard which I sifted before use