Air Pressure?

[Raymond Chapman]

We've just received our order of silicon carbide and are ready to do some glass etching using this rather than aluminum oxide.

What should be the psi using this new aggregate?

[Danny Baronian]

If your frosting or etching, 30 to 40 psi.

Do a sample and adjust as necessary

[Raymond Chapman]

Thanks Danny.

Wow...what a world of difference between aluminum oxide and silicon carbide. And you get a little light show, too.

[Kelly Thorson]

Wow...what a world of difference between aluminum oxide and silicon carbide

Can you expand on that Raymond?

[Dan Seese]

Kelly,
I'll let Raymond speak for himself but there are a couple of nice features about silicon carbide.
For one thing, aluminum oxide, which has a brown color, seems to cling to everything including the back of the glass. You get some of this with silicon carbide, but not that much.
Silicon carbide is black in color and is sharper and harder. Norm and Ruth Dobbins have a chart in their book, "Etched Glass", which compares several abrasives. Here is what they list as the advantages of silicon carbide:
"Cuts glass most quickly of all abrasives. Produces very little static electricitly. Cost per hour comparable to aluminum oxide. It can be recycled almost indefinitely since particles break along crystaline cleavage planes, always leaving sharp corners and edges. Because there is no free silica in the dust, it is much safer to use. Causes a flashlight effect during blasting, illuminating the work surface."
One of the disadvantages they site is that because of it's sharpness it wears out nozzles faster.
The "flashlight effect" is a sparking action that happens when the medium hits the glass. Actually helps you see where you're blasting.
Anyway, it is the abrasive I use for most of my glass work. (I thought it interesting that Larry and Doug - his partner at Milestone Manufacturing and a great glass artist - use various abrasives, depending on what effect they want to achieve. I think I'll try out on my glass some of the courser sand I use for sandblasting foam and wood.)
Raymond, if you want to carve the glass, you can turn the pressure up pretty high. I know I've done it at 65 psi & higher, but it's probably better to stay around 40 where you'll have more control. You just need to watch yourself and keep it consistent or the uneveness will show and can't be corrected. And of course, the distance you hold the nozzle from the glass and the speed you move it will all affect the end results.
I've also blasted at pressure as low as 4-5 psi when doing some shaded etching - a very light "airbrushed" effect. (Doug had a really cool Pasche "eraser" which does a nice fine shaded effect and it seems to me that he used a pretty high pressure with it.)
Well, I hope I didn't give too much misinformation here. Sometimes I don't know when to shut up.
Dan

[Raymond Chapman]

Kelly, Dan's answer is much better than I could have done.

One of the first things we (Mike, my son and me) noticed was how quickly it etched the glass. Mike actually is the one doing the etching....I just stand around and watch. The silicon carbide carved deeply into the glass with little effort and without the dust that is usually generated with aluminum oxide or sand.

Even though the silicon carbide is more expensive, since it etches so quickly it is actually saving us money.

The sparking effect is really neat. It's almost like a small laser beam hitting the glass.

We also had discovered that with the aluminum oxide sometimes the mask would fail and we would get some blow-by or small specks where the mask became thin....and it wasn't noticeable until the mask was removed. We are using Gerber Mask II and the deep carving with aluminum oxide was just too much for the mask to withstand. This only happened in a very few spots. Possibly because we stayed in one spot too long and the glass heated up.

Mike is really enjoying our new discoveries with glass. We are doing more and more of this type work as the local glass companies know that we can produce this stuff locally.

[Kelly Thorson]

Thanks Dan and Ray,

I haven't been able to source the silicon carbide here yet, but I think I'll make a bigger effort. Sometimes I'm too lazy.

I'm just starting to explore the world of etching and carving, I think it is one I'm going to like.

I'd heard that there was less static, and that aluminum oxide could interfere with solution gilding if you didn't clean it properly. This adds to justifying the added expense.

[Raymond Chapman]

Kelly - I wasn't able to find any locally, but ordered mine from Norm Dobbins in Santa Fe. He has all types of supplies - even classes.

505-473-9203
www.etchmaster.com

[Danny Baronian]

Make sure to check this page out for supplies:

http://www.theletterheads.com/supplies/index.htm

The following information is listed on that page under smalts, also know as black beauty and klean blast. I don't know the name of the company, but the numbers are for the same company, different locations. They are an industrial supplier of abrasives and related products. Check with a local body shop supply, many times they carry a limited stock of abrasives. If they don't, ask for a local supplier. Might as well get it local, shipping costs are going up.

Smalts-Kleen Blast Abrasive
Kleen blast comes in 50 lb sacks and costs around $ 5 for the bag.
5 grit sizes ranging from 8-12 grit to 30/60 grit. The 35 grit matches up exactly with smalts Rick sold.
California - North (Hayward) 800 227-1134
California - South (San Diego) 619 239-1092
Washington (Tacoma) 800 228-4786
Oregon (Portland) 800 634-8499
Canada (Grand Forks B.C.) 250 442-2260

In addition, this company carries silica, aluminum oxide, silicon carbide, garnet as well as others that aren't suited for glass work.

The cost for silicon carbide is deceiving. While it cost more than other abrasives, it will last 10 - 20 times longer or more and still be as aggressive as new material.

If you use silicon carbide order some carbide tips from Glastar:

http://www.glastar.com/

The tips are more expensive, but they last about 5 times more than ceramic.