Sandblasting followup...

[4mikee]

Instead of taking the old thread I'll start another. Recently I posted a question about sandblasing bowls. I purchased a cabinet from HF large enough to do some large pieces and the quality of the cabinet is good considering. Now the real reason for the post is for me to clarify some things about the technique and I may repeat some of the past info so please excuse me.

When spraying should there be a high pressure spray? I'm using glass bead and it is extremely slow and not a lot of pressure at 100 psi. I can hold the nozzle almost directly on the piece and not get an effect. I imagined it some what different. It would probably take a couple of hours to get a suitable effect on the piece of cottonwood I'm using. I'm not going to try it but i believe I could almost do away with the gloves. Something doesn't seem right.

Thanks for any help.

 

[Bob Chapman]

Hi Mike,

I can't offer any help I'm afraid, but your description fits my experiences exactly. I got nowhere fast! The only bits I can add are that I was using sand, and that when I tried it on glass rather than wood, it seemed to work perfectly and etched the glass with no problem at all. I put it down to the fact thar wood is softer and less brittle than glass, but I don't really understand why it didn't seem to remove the wood, and will watch this space with interest.

Bob

 

[Donna Banfield]

Bob and Mike, there are other forms of media that are more aggressive. Black Beauty, or Black Diamond (trade names) are both very aggressive media, and will etch the wood quickly -- by that I mean it won't take an hour to see any results. The down side to using this media is that on lighter woods, it will be blown into the pores and grain and stay there -- and you will see the dark color.

I also know that after awhile, the media will wear down; the cutting or etching is created by sharpness of the edges. No media will last forever, and glass bead is not as aggressive as others. If you've been using it for awile, it may have simply lost it's cutting edges.

Having a big enough compressor is essential. You want to push/force the media with as much pressure as possible. I had dismal results using a small Porter-Cable compressor, which was fine for the brad nail gun, but ineffective for etching wood, regardless of the media.

I've never turned cottonwood, so don't know what it's like to sandblast. The only woods that I've put in the cabinet are open grain, like ash, oak and walnut. The blasting/etching is done in the softer areas between the rings, where the wood is removed, enhancing the appearance of the 'rings'.

 

[Joe Greiner]

Many, many, many years ago, I worked in the precast architectural concrete industry. For sandblasting, we used a product from (IIRC) Pennsylvania Glass Sand, or something like that. The sand was white and quite coarse. I don't know if they're still in business; I assume they were/are in Pennsylvania; and they might have finer grit suitable for smaller machines.

Commercial sandblasters/signmakers in your area might be willing to share their secrets, if they don't perceive you as a business threat. Worth an inquiry, at least, even if they tell you where to go (interpret this two ways).

Joe

 

[Pascal Oudet]

Mike,
glass beads are far less agressive than other blasting media. they are more round, less sharp, and are good for surface cleaning, but not for material removal. and they are also more expensive than other media.
I use a aluminum oxyde based product (black) or corundum (sp?) (what white grinding wheels are made of).

Pascal

 

[Bob Chapman]

Thanks to all above for the advice. I'll investigate what abrasive media are available here in the UK and have another go.

Bob

 

[Malcolm Tibbetts]

Mike, my sandblasting experiences are quite limited. I once borrowed some large industrial equipment and did the blasting outdoors. I wore a full suit, etc. I blasted soft redwood segments which were surrounded by hard maple. I can tell you, that the material removal was extremely fast. In some cases (intentionally), I eroded most of the redwood away within seconds, leaving a framework of textured maple. I believe that I used #30 sand.

 

[4mikee]

Ain't posting great. Thanks everyone. I'll spare you a bunch of quotes but would like to respond.

Donna thanks, the cottonwood is softer than the oak and appears to have minimal soft grain but I didn't mind sacraficing this piece. Lots of time spent with glass bead and little to show.

Pascal thanks again for the response. I was hoping you and Donna would chime in.

Sounds like I'm not the only one in this boat so company is always nice.

I compare the effect I'm after to Pascal's work since it is in line with what my minds eye sees at this time. Lot's of textures and possibilties. It's wonderful work and if you have time check it out.

I am searching now for corborundum (sp?). Last night I purchased Garnet and it was listed as more agresseive than glass but the color was a reddish brown which would have helped. After trying a little it wasn't any better. I'll go back today and get the aluminum oxide although it was black. I'm not giving up on the corborundum, I'll try the monument companies. I'll post back in a day or two what I came up with. By the way I think I saw on Bill Luces' site a photo of the black embeddeded in the grain and it actually added to the piece. (Hope may memory served me well). His pieces had some nice embellishment from sandblasting.

Thanks All,

 

[michael h]

I've been using crushed glass , which works great and it one of the less expensive media I've found. It doesn't last too long but I get a fair amount of blasting done before it needs to be changed.
http://www.grainger.com/Grainger/items/6ZC15
I get it from Grainger

Good luck,
Michael Hampel

 

[4mikee]

I'm having trouble finding time to experiment and report back as I said I would. I did pick up a bag of black beauty and tried it on the ne cottenwood. This did make a difference, however it didn't strike me as being on the high end of aggressive. I also picked up a bucket of aluminum oxide but at the checkout I realized black beauty is much less expensive. As stated from others, the coloration the darker grit leaves make some finishes unlikely. Pascal suggested Corundum but I can't find it locally. I'm still working at it. Maybe we need Donna and Pascal to have an online symposium....that's a thought.
No turning for a week or so, I'm going to the gulf coast to help the storm make landfall.
Thanks
Mike