December '20

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5 6 G R A P H I C S P R O D E C E M B E R 2 0 2 0 G R A P H I C S - P R O. C O M Either of these abrasives are excellent choices. Both materials are hard minerals, with silicon carbide registering a 9.5 on the Mohs hardness scale and the oxide at a 9. The hardest substance, diamond, is a 10. Your decision of which abrasive to use depends on the cost effectiveness of each one for the job, your blasting equipment, technique, and use. COST EFFECTIVENESS The cost effectiveness of an abrasive is a measure of how much glass you can etch per dollar spent on abrasive and labor. The more efficient (faster) an abrasive is, the lower the labor cost to produce an etching. The more times you can recycle an abrasive without losing etching speed, the lower the abrasive cost (if the abrasive loses etching speed with continued reuse, the labor cost necessarily goes up). The equipment you use is important because that determines whether or not you can recycle the abrasive. If you have a good blast cabinet or blast room in which to etch, you can use any of the abrasives that can be recycled. Abrasive Types and Characteristics ABRASIVE TYPE USES OTHER FACTS Aluminum oxide Grit sizes: 12 –1,500 Glass etching, stone and wood blasting, metal finishing; manufacturing sandpaper, grinding wheels Very hard, tough abrasive that cuts glass quickly. Major drawback: generates static electricity, which causes dust to cling to the the back of glass being blasted. Makes it hard to see what you are doing if you prefer lighting the glass from the back. Brown is most common and cheapest. White and pink are available: higher purity and cost but no increase in speed. No free silica. Silicon carbide Grit sizes: 12 –1,500 Glass etching, metal finishing; manufacturing sandpaper, grinding wheels, non-skid surfaces (can be used on stone and wood) Harder than aluminum oxide; cuts glass faster because it constantly breaks off small pieces, exposing new cutting edges. No static electricity. No free silica. Creates "flashlight effect": small sparks where particles hit glass, making it easy to see area being blasted. Black is most common; green is sometimes available and is slightly harder but costs much more. Cost Effectiveness of Abrasives TYPE OF ABRASIVE ETCHING SPEED NUMBER OF CYCLES COST PER 100 POUNDS COST OF ABRASIVE USED IN 50 CYCLES (100 LB. QUANTITY) APPROX. COST PER HOUR OF USE Brown sand Medium slow 2 $5.00 $125.00 $1.25 White crystal silica sand Medium slow 2 $5.00 $125.00 $1.25 Garnet Medium 4-8 $25.00 $150.00 $1.50 Aluminum oxide Medium fast 60-80 $100.00 $63.00 $ .63 Silicon carbide Fast 80-100 $150.00 $75.00 $ .75 Please note: 1) Cost figures are approximate and will vary with different suppliers. Figures for number of cycles vary with the type of blasting done and the technique of the person doing the blasting. 2) The number of cycles for all materials except carbide depends on how quickly the particles get dull (i.e., how hard the material is). Carbide never gets dull; it just breaks down into finer and finer particles. As the particles get smaller, more are sucked out of the cabinet by the dust collector. With a stronger vacuum system, you get fewer cycles per pound of grit (although there is less dust to obscure vision). 3) Based on estimated average of two hours per cycle, 100 pound quantity. Sandcarving Systems SR3000 TM Self Stick Photoresist Film 800-729-9478 3 Easy Steps Automatic Washout Systems

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