sandblasting

lohman · Post by **lohman** » Sat Feb 21, 2004 8:09 am

I'm looking for an alternative blasting medium to the silicon carbide I usually use. I'll be renting a pressure pot and compresser. The guy at the rental says I can't recycle the medium because it might damage the pressure pump. I told him I was going to do the work in a clean enviornment (you know, be very careful using drop cloths and sift the blasting medium before re-cycling etc.) He said NO. He sent me to a farm supply store that sells sand for sandblasting. They carry a OO size sand and to me it looks too large a particle size compared the the silicon carbide. I'll be using 5 mil stencil from Photobrasive and need to hold a halftone at 25 lpi. Any suggestion?
Thanks

scooter riegelsperger · Sat Feb 21, 2004 9:11 am

try 50 grit aluminum oxide.

Larry Lunsford · Post by **Larry Lunsford** » Sat Feb 21, 2004 11:57 am

If by pressure pump you mean air compressor, then the rental guy advice in nonsence. The blast media never goes through the air compressor.

As for recycling the media, unless you use a blast cabinet the media is going to go everywhere in all directions. There won't be anything to recycle.

You should be able to get relatively fine sand from Lowes, Home Depot, etc. Look in the area with concrete and mortar. I've used the sand packaged by the concrete company (Quick Crete I think) that's labeled as medium, but is actually fairly fine.

If you look in the Yellow Pages under sand blasting, you should be able to find companies that will sell a variety of other medias.

If you're blasting in the open, be sure to wear a respirator. A bunny suit or at least a hood will also help keep the media out of your personal crevices. From my personal experience, I'd say that the best way to recycle media when blasting in the open is to collect the stuff that accumulates in your butt crack (How does it get there?!).

Avery Anderson · Post by **Avery Anderson** » Sat Feb 21, 2004 11:59 am

Get some aluminum oxide, but not 50 grit, it is way too coarse for using with photobrasive. I'd suggest 150 or 180.

Avery

Tony Smith · Post by **Tony Smith** » Sat Feb 21, 2004 1:30 pm

You should go out and buy the small pressure pot from Harbor freight or northern tool for about $100. They work great and nobody will tell you that you can't recycle your sifted abrasive through it.

Tony

Greg Rawls · Post by **Greg Rawls** » Sun Feb 22, 2004 11:12 am

Word of advice about using sand in a sand blaster. Sand contains crystalline silica. Significant exposure can cause lung fibrosis and/or silicosis. Both are pretty awful lung diseases. Recommend that you use either aluminum oxide or silicon carbide. Both are considered to be nuisance dusts by OSHA. If you feel you have to use sand, make sure that your cabinet does not leak, avoid exposures (dust control system) and please wear a P100 (HEPA) respirator. A regular dust mask is not good enough.

Greg
http://www.gregorieglass.com

Mark Hughes · Post by **Mark Hughes** » Sun Feb 22, 2004 11:38 am

If you have access to Harbor Freight they have pressure pots ( 20 lb. 59.99 , 40 lb. 79.99 ) on sale. harborfreight.com

lohman · Post by **lohman** » Tue Feb 24, 2004 6:50 pm

Thanks everyone for your advice. I hadn't responded because I was having major problems with my computer. (it's always something, isn't it?)
I have shopped at a local tool rental that sells it's "retired" equipment, and what I saw there and what I was told is that I will need no less that a huge monster tank and compressor. I'm not going to sandblast bridges or ships so I will take the advice about the smaller units available from Harbor, etc.

lohman · Post by **lohman** » Tue Feb 24, 2004 7:25 pm

Mark Hughes:
I just surfed over to Harbor Freight and those smaller pressure pots are very interesting. Do you have personal experience? I want to be able to do both light etching, deep carving and all the way to cutting through 3/4 inch glass. I had a local shop do a test cut for me and it worked so well I have trouble settelling for anything less (short of shelling out thousands of $ for those monsters that will eat up my limited space not to mention $.)

Thanks!

charlie · Post by **charlie** » Wed Feb 25, 2004 10:19 am

lohman wrote:Mark Hughes:
I just surfed over to Harbor Freight and those smaller pressure pots are very interesting. Do you have personal experience? I want to be able to do both light etching, deep carving and all the way to cutting through 3/4 inch glass. I had a local shop do a test cut for me and it worked so well I have trouble settelling for anything less (short of shelling out thousands of $ for those monsters that will eat up my limited space not to mention $.)

Thanks!

i have the 40 lb pressure pot from hf. it works well, but you have to put it together, and if a fitting leaks, then you have to take it ALL apart to fix. also, the gun could use some work as it's not of the best quality.

do NOT get a small hf central pneumatic compressor. get a brand name one instead. the hf brand is imported, very hard to get non-standard parts for, and won't last very long.

you can get blasting grit at hf pretty cheaply.

lohman · Post by **lohman** » Wed Feb 25, 2004 9:08 pm

Hey all,
I just talked to a man with 50 years experience sandblasting monuments.
He says the small 15 lb pressure pots are good and you can do a lot of work with them but the critical factor is having a compressor that delivers a minimum 35 cfm continuously. So it's the volume of air that is important more so than the psi rating. At least that is my understanding.

Ron Coleman · Post by **Ron Coleman** » Wed Feb 25, 2004 11:10 pm

lohman wrote:Hey all,
I just talked to a man with 50 years experience sandblasting monuments.
He says the small 15 lb pressure pots are good and you can do a lot of work with them but the critical factor is having a compressor that delivers a minimum 35 cfm continuously. So it's the volume of air that is important more so than the psi rating. At least that is my understanding.

Need a reality check on this one.
35 cfm is a MONSTER compressor, probably cost you about $10,000.

hoknok · Post by **hoknok** » Thu Feb 26, 2004 1:37 am

Need a reality check on this one.
35 cfm is a MONSTER compressor, probably cost you about $10,000.

For real! I read that and thought, Damn, I have never seen one that big before. Maybe he ment that the pressure pot needs to output 35 CFM? Even then, that seems high.

After all, isn't that the reason for a pressure pot anyway, to increase the CFM without having to spend major bucks?

Mike

Tony Smith · Post by **Tony Smith** » Thu Feb 26, 2004 4:46 am

Let's see... at 35 CFM (constant supply) that's 60,480 cubic inches of air per minute or 3,628,800 cubic inches of air per hour through a 1/8" diameter nozzle which has a cross sectional area of .01227 sq inches. That gives us an air velocity of 295,701,475 inches per hour or 4667 miles per hour... we might be able to knock down a patriot missile with abrasive traveling that fast...

Keeping below supersonic flow requires only 5 CFM. I think someone was blowing smoke up your butt... or he uses a 3/8" ID nozzle

Tony

lohman · Post by **lohman** » Thu Feb 26, 2004 8:11 am

You guys are right. It takes a MONSTER to do the cutting I want to do.
There has to be a compressor out there that is scaled to the needs of someone who isn't necessarily going to sandblast bridges and ships and who only wants to cut AWAY some glass.

I had a shop test-cut a piece of 3/4 inch glass and the guy cut through in about 10 seconds.

I'll post a picture on my yahoo photo album under "Sand Cutting"

<http://photos.yahoo.com/eugenelohman>

lohman · Post by **lohman** » Thu Feb 26, 2004 8:28 am

Oops!
Having technical difficulties with photo album...stay tuned.

lohman · Post by **lohman** » Thu Feb 26, 2004 10:08 am

Try this to see my sample of 3/4 inch glass cut through with high pressure sandblasting

http://photos.yahoo.com/eugenelohman

or:
http://f1.pgphotos.yahoo.com/ph/eugenelohman/my_photos

hoknok · Post by **hoknok** » Thu Feb 26, 2004 9:19 pm

So what isss the proper mixure of pressure to sandblast glass?

lohman · Post by **lohman** » Thu Feb 26, 2004 10:32 pm

I think the proper pressure depends on the end result you're trying to achieve.
If I want to surface etch I don't need much "pressure". I use about 100 psi but I'm only putting out about 12 cfm (cubic feet per minute.) The heavy duty sandblasting that requires deep and even blasting through the glass requires both high psi and high cfm. My set-up will blast through the glass but it takes way too much time to do. I'm talking frustrating hours to accomplish what the proper set-up will do in a few minutes.

Were you able to see my photos? I can e-mail a jpeg or two if you can't access my yahoo photo album.

Lynne Chappell · Post by **Lynne Chappell** » Fri Feb 27, 2004 1:00 am

Well, my 15 HP compressor puts out 41 cfm. The nice industrial 5 HP compressor that I used to use (a real 5 HP, not the hobby kind), only put out 17 cfm. That was really borderline to power a 100 lb pressure pot. So of course we went to overkill on the upgrade, but it hardly ever turns on, even though we have a 200 lb pot and an air hood both running from it.

The problem with the small pots is that you keep having to stop and refill the pot if you're blasting larger pieces of glass.