Question: Air Easer Grit

[Marrinan]

Hell-o All, I had occasion to be at VA in Tallahassee today so went by Harbor Freight and picked up a Central Pneumatic "Air Eraser Kit". It came with a small quantity of blasting media (150g) of BD-60. A looked at the other blasting media they had there and 2 lbs. of White Aluminum Oxide Abrasive. They had things like glass beads, silica sand, soda (baking I think) walnut shell, several kinds of coarse what looked like pumice. When blasting on coins or silver on which a satin finish is desired which media should be used.

When covering surfaces to protect from blasting do you suggest frisk-it or rubber cement or clear tape, clear contact paper. any advise would be appreciated thanks Fred

 

[Keith]

For my hobo nickels I use aluminum oxide abrasive from Paasche it has aex in big letters on the container there is no grit size. It gives a nice gray tone to the coins.
Badger makes this grit too but Ifound it a little too rough for coins.
For masking coins that I dont want blasted I paint clear nail polish on the part I dont want blasted. After Im done I use nail polish remover to take the clear off. I use this If I want say the hatband on a coin to be shiny and the rest to be dull gray. I tried baking soda as a blast media and baby powder too but it ran through the air eraser too quickly. The aluminum oxide stuff was the best.
Good luck,
Keith

 

[Marrinan]

Thanks a bunch Keith. I would not of thought of nail polish. Used to use contact paper and rubber cemment for airbrushing motorcycle tanks in the day. Thanks again for the grit advise as well-Fred

 

[KCSteve]

I picked up a Paasche air eraser and found that the grit I had around was too coarse for it so I ordered some direct from Paasche (couldn't find it in town). Got the 6oz size of all three grits.

Tried the medium (AE) today - that stuff is fine! A very light and fluffy powder that flows quite easily and well. Did some test blasting to get things set about right. By working close to the coin (about 1/8") you can hit just a tiny spot.

 

[Dave London]

Scotch magic tape works fine for masking , I use a exacto knove under the scope to cut away the parts to be blasted.
Grit depends a lot on air pressure most of the hobby guns are limited to about 30-40 psi and al oxide works great. Glass works good also but at higher psi

 

[Kevin P.]

Fred it depends on the effect you're after.
Aluminum Oxide is a cutting agent and coarser grits leave a more noticeable effect than the finer grits.
Glass beads leave the softest finish. One point about glass beads is that if the pressure is too high the beads break and will not have work. They require a lower pressure to get the effect that glass beads are known for which is the softest.

Lapidary places will have many similar things. The difference in price is often due to how carefully graded the material is. This careful grading may not be important for your purposes.
Some of those other things are used by auto restorers, some others for reloaders.
HTH

One last thing is the pumice. It's finely ground lava. It has a nice effect you might like and it's easy to use. I use an old soft tooth brush; dampen it enough to hold the pumice and just brush it across the metal. If you like the look it's very simple, no tools.
Kevin P.

 

[Tim Wells]

I have one of those and I tape off things with Scotch "magic tape" and cut the blast area out with a scalpel. Whatever you do, do it outside or grit will be in every nook and cranny of your shop. Learn from my mistake.

 

[Billzach]

I never mask or tape any area of my coin carvings. I blast the whole coin and then use a old toothbrush and finger printing ink to get the effect I want..

 

[dhall]

This is a slightly different slant, but I'd done some sandblasting on stone for a buddy of mine. He used rubber cement to affix his paper pattern on to a piece of sheet copper, and then he cut out the pattern using a jeweler's saw. I taped the copper stencil on to the flat stone surface with masking tape and did some fairly deep-relief sand blasting with 60 grit aluminum oxide. I sandblasted about a half-dozen pieces for him, and I was amazed at how impervious the rubber cement was to the grit. After quite a bit of blasting, the area underneath the rubber cement was untouched.

It'd probably be a pain to try and paint/control rubber cement on to something with as small and delicate a pattern area as you might find on a coin, but I was mightily impress with how well rubber cement resisted the abrasive influences of sandblasting.

Best regards,
Doug

 

[gtsport]

I use liquid rubber mold maker from hobby lobby as a sandblast mask. I apply it with a toothpick for accuracy when I want a frosted effect on the coin dies I cut.

Joe Paonessa

 

[Marrinan]

Thanks to all-Great information from all I think I will try them all-Thanks for taking the time to help Fred

 

[Dave London]

Fred
One more thing do not try to use abrasive blasting on assembled guns, folding knives etc Don't ask how I know this.:beat up:


Help I am a tool addict

 

[CJ Tate]

Thank you all for this information. I have printed it off for my notebook.

Dave - thank you for final tidbit. I am just inexperienced to try something like that!

 

[Marrinan]

Come on Dave there must be a story-good sound reasoning than you- Fred

 

[Dave London]

Fred
Lets just say that the grit is so fine you cannot keep it out of the places you dont want it