Sorry, no photos boys and girls. You'll just have to use your imagination, but I've tried to break it up into bite-sized chunks. This is in the words of my brother, a gl*** sculptor, who has cut a few windshields in his day. Without further ado... Sand blasting windshields. It all comes down to safety laminate or tempered. If it’s tempered it will go BOOM no matter what you do. If it’s lammie it just takes time. Cutting flat gl*** you can use the gl*** cutter and lighter fluid method, but that's lousy for cutting curved gl***. I’ve done a combination of both, blasting to the laminate from both sides then a combo of cutting and burning. I’ve also done just blasting and cutting. The problem is that the laminate is a resist, and a tough one at that, so blasting through it is a pain in the ***. So here we go... blasting through any piece of gl*** is just a matter of method, and PATIENCE. Masking: ("resist" is like masking tape for sandblasting) Duct tape is a useless resist as it’s mostly fibre. You want rubber or vinyl or plastic. Ideally you mask off almost all your window (on both sides) with something simple like clear shelf liner (MacTac), leaving about a 1/2 inch back from where you want to cut. This just protects the gl*** from overspray and scratches but doesn’t need to be heavy duty. Nor does it need to be clear but I find it easier to pay attention to what I’m doing. Do watch out for heavy duty adhesive as it’s a ***** to take off big sheets of mask when it’s fighting back. Overlap the MacTac with electrical tape or (funnily enough) sandblast tape (available from a lot of sign making, auto customizing shops or online). Venture Tape is a good one and comes in various widths, from pinstripe to 6”. Cover past where you do want to cut and then cut away the part you don’t want, creating the edge of your windshield. If you use electrical tape or some thin equivalent you’ll likely want to use at least 2 or 3 layers as you’ll be cutting, not just frosting or carving, and your grit will eat your resist. Make sure you tape all around your other edges too so as to not have them lift from overspray. Blasting media: When you go to blast use a fairly fine a grit if possible, ie 100 or 120, and preferably aluminum oxide - NOT sand. A lot of commercial “strip ‘em” blasters use much courser grit (60 or 80) and it’s like throwing rocks. Then again super fine like 200 and up is too fine for cutting, and gl*** beads etc are useless. Air Pressure: You want to blast about 80 psi if possible. Most siphon systems only go up to 60psi at the nozzle, no matter what the compressor may be throwing, so will take much longer. Pressure pot systems are the way the to go if possible. Nozzle: Use a fairly fine nozzle; 1/8” ideally so you’re actually creating a cutting tool not just a spray. Ceramic nozzles burn out fast; have a few on hand (they’re usually about $5 - $10 bucks). I can go through a ceramic nozzle in about 3 hours at 100 psi. (That’s why I use $300 boron nozzles; and still only get about a year out of them). Cutting: Heat build up is your enemy so you want to keep your nozzle moving. Just keep doing back and forth p***es of 3 or 4 inches at a time, keeping the nozzle about an inch from the surface and angled slightly away from the tape so it doesn’t undercut and lift it. Be patient: For a windshield you’re looking at an hour a side, erring on the cautious side. By going back and forth along the length of your cut like you want to etch a trough before you try to cut through. That way if you start a “run” (a moving crack) it’ll follow the already cut area (in theory) rather than zooming off into parts unwanted. So just work your way back and forth from one end to the other until you encounter your laminate (you’ll know; you’ll suddenly be seeing blackening plastic). You want to cut through the gl*** using a “connect the dots” technique, ie. as you encounter your lammie move along and continue somewhere else until you get the same thing happening. This is again to prevent runs. With normal gl*** this is pretty tricky on long pieces as the pressure can cause the top part of the gl*** to flip off taking chunks with it. With a laminated windshield the lammie holds it all together, but be careful of the waste-side of the gl*** flopping around and creating weight and pressure. You’ll find it best to have your gl*** clamped on some kind of rack or support frame, preferably with a support bar just below your cut line to relieve torque. Work your way back and forth until you’re through the whole thing, doing the “connect-the-dots” until the whole thing has been pierced on the one side. Take it out, flip it over, reclamp, and repeat. This time you will want to clamp the top part too so it doesn't torque back and forth and crack the uncut parts. Cutting the laminate: Now that you've blasted through to the laminate on both sides you can carefully cut the laminate with an Xacto. Again, be patient and take your time. Many light cuts is better than one heavy cut. It’s easier than it sounds; just not something that translates into words well. Hopefully this makes some sense. A lot will depend on whether you’re renting a booth or a cabinet as it’s a hell of a lot easier to do big gl*** in a big environment. ———— You're done. Easy as duck soup. Get out there and get cutting. Hope this helps someone.
This is good Tech......Don"t rush is, take yer time. When ya get the finished size, good idea to grind the edge and remove any sharp edges. Glaizers call it "Seaming" any flaw will be a weak spot, for a crack to start. Good post!!......OLDBEET
good post. Thank you. Any one ever use a laser or hi pressure water to chop a windshield? If, you did, any info on the process will be appreciated, positive, negatives, success or failure. Not looking for pro and con opinions, educated or non educated guesses just real, factual experience. Thanks.
The Jalopy Journal
