Recommend an aluminum oxide grit

[Jthompson1995]

I have been using fine glass bead in my sandblaster with mixed results, partly because of differences in the wood and partly, I think, because I am using a smaller compressor and small (5cfm) nozzle. My intention is to find a harder abrasive to blast harder blocks better and possibly speed up blasting since I'm using a smaller nozzle.

I am thinking to get some aluminum oxide to mix with the glass bead or use by itself but don't know where to start grit wise. My current thought (guess) is to try some 220 grit to see how it goes. Does this sound reasonable or am I way off base here? If this is off base should I go coarser, finer?

I am planning on experimenting with pressures, distance, mixing, blasting separate with alox then glass bead for detail etc, I'm just trying to not spend a lot of money on some media I can't use and it go to waste.

Thanks in advance.

[scotties22]

I have the same compressor problem. I have always mixed the small tub of 220 AO from Harbor Freight in with my extra fine glass beads. I get somewhat of a noticeable difference in cut, but it still takes me forever to sandblast a pipe.

[sandahlpipe]

What kind of blast cabinet are you working with? I found that my blast speed went up significantly when I switched from the harbor freight blast cabinet to the Cyclone e100.

But as far as blasting is concerned, the real way to go is to get a compressor with enough power to handle the task. Aluminum oxide will indeed take off material faster than glass bead, but it's also going to decrease detail which is very likely not what you want. Using an under-powered compressor will cause endless frustration when blasting because you'll constantly be waiting for it to catch up, and even when it's full, you barely have enough CFM's to pump out the blast media.

If you want to experiment with adding alox to your glass beads, it's worth a try, but chances are it's not going to get you where you want to be with a nice, detailed blast.

[Jthompson1995]

Thanks Scottie & Jeremiah.

To clarify a bit, I understand that the alox will not be as detailed as the glass bead but I am thinking it may get the blast a little deeper to begin with then I can follow up with just glass bead for the detail. I am using the cyclone e100 cabinet with the 5cfm air nozzle and the smaller size ceramic nozzle for the gun. Those changes did greatly increase the performance of the setup. Unfortunately it will be quite a while until I have the funds and room for a large compressor.

I have been able to blast a couple pipes in just 20-30 minutes but I've found that when I blast some blocks with just the glass beads the straight grain in the block has some harder "rays" that don't want to go away and it significantly reduces the appearance of the ring grain. I am hoping that a harder, sharper abrasive will be able to help define the ring grain first then I can get the detail with the glass bead. I know it's a bunch of changing out abrasives but such is life.

As long as I don't get a resounding "that won't work, I tried it already" I'll get a smaller amount and see how it goes.

[Sasquatch]

Really, PSI lacking, you won't get detail, I don't care if you blast with ground Unicorn horn.

You can try al/ox or si/car and see how it cuts, but you are likely to find that it just washes away the pipe at a faster rate unless you have the proper pressure in the system to begin with.

[oklahoma red]

As Paul Harvey used to say: "I'm going to tell you more than I know". I don't know exactly what effect you are striving for but blasting is still one of the dark arts. I am not a big fan of the really deep, craggy effects (ala Cooke and Roush et al). It is my understanding that these are achieved by multi-stage techniques with different media (and different parameters with each) and that one of the final stages is "chasing" the grain with a small pencil blaster and the end result takes a lot of time. My personal preference is a blast that reveals good definition but is not so deep that it becomes a lint catcher. In my own experience I find the piece of briar itself is one of the biggest variables and with it, learning to read the grain. Grit and pressures and tip sizes are some of the things that the really good blasters are loathe to give up. I attain what I'm looking for with fine glass beads, 100 psi and a 1/4" nozzle. My compressor is a 6 HP Kaeser with a 60 gallon tank and I have no waiting. You're going to have your work cut out for you in juggling all the variables, including the briar, to get what you are looking for. But, that is the way to do it. According to Premal: TIAFO.
Yet another variable is the usage of a pressure pot. Generally speaking this will put a lot more media on the part at less pressure thru the nozzle. If Chris is listening from across the pond: do you have anything to report on your recent acquisition of a pressure pot?

[caskwith]

Good timing on my part to check the forum.

Pressure pot has introduced a whole new learning curve for me. My old system was just a simple siphon, my compressor had no trouble keeping up with me, though it was running for a large portion of the time I was blasting, it was delivering the air required. The pressure pot is slightly different, the compressor has no trouble providing the pressure (it actually runs much at much lower PSI), the problem is volume. The PP requires much more volume of air to run, I had to upgrade my hoses to larger diameters as using the old hoses it just couldn't keep up, the hoses physically could not provide the air required. The new hoses work much better and if I get my air/media/pressure mix just right then I can blast until the media runs out.

What I have discovered so far (I have only blasted a few times since getting it all running properly) is that a PP system is much faster at removing material, in fact you can easily blow a hole clean through the wood if you wanted, but it takes skill to get the detail. It does seem to be less fussy about the briar so sandblast quality will now be less of a crap shoot when it comes to the wood.
A PP is not really suited to morta or strawberry wood, it's too aggressive so I will be sticking to the old siphon system for doing those pipes.

Time will tell how the PP works out for me, I have a very small amount invested in it, so that takes the pressure off getting good results (pun intended) and it will probably be at least a year before I can be confident in it's use. Most likely outcome at the moment is that I will use the PP for an initial blast of briar pipes only, get some depth going quickly and efficiently, then I will switch over the siphon system and use that to tidy things up and get a bit more detail, as well as doing my morta pipes etc.

Anyway we'll see, be interesting to look back at this in a year or two and see my thought then.

To sum up briefly for someone new to sandblasting, DON'T get a pressure pot, it is simply too complicated and too frustrating to use if you don't already have a few years of siphon blasting behind you.

[Jthompson1995]

Thanks for the info everyone. It is very helpful. I think I'll give it a go with the 220 grit and see what happens.