Poor Man's Air Blaster

[TOM BUCKLEY]

Try this link:

https://picasaweb.go...JO1qsHurY6UqgE#

Tom

[oilshale]

The topic should be: Clever man's air blaster!

Thanks Tom for starting this great thread!

Thomas

[TOM BUCKLEY]

The topic should be: Clever man's air blaster!

Thanks Tom for starting this great thread!

Thomas

Thomas,

Thanks. You are very welcome.

Tom

[Herb]

Just for fyi,I bought a nice air blaster tank from Harbor Freight with about a 2'x2'3' metal cabinet, interior light , glass top and attached rubber gloves and nozzle ans sphon for $150, add a compressor and shop vac and you have a nice blast cabinet for about $300 bucks.

[squalicorax]

Any reccomendations for a type of pan to use to "bake" my dolomite powder. Just got a fresh load in the mail today but both containers are pretty moist and they are having trouble blasting. Would glass be fine?

[Malcolmt]

Depends on the type of glass. If it is pyrex then it would be safe. I just spread it out on a metal cookie sheet about a pound at a time and bake at 250 I usually leave in for 20 minutes longer if I forget to take it out. Once baked and cooled a bit I have a plastic bottle with a tight cap that holds about 2 pounds. I screen it through a 120 mesh before putting it in the bottle. I never keep more than about 2 pounds made up at a time as it does re-absorb water. FYI I have already screened and separated out using 50 then 80 then 100 then 120 the 200 then 320 when I get the dolomite. I add a 30 mesh to the stack if I am resorting the used material as it picks up the bits that got knocked of fossils that I cleaned. I then look at what did not go through the 30 mesh under my scope and often find missing bits that got knocked of trilobites that I can re-attach.

The big 50 pound bags I can get up here in Canada have dolomite particles sizes ranging from 60 mesh to sub 320 mesh. I also have some dolomite from Paleotools that is uniform 44 micron. This is about 320 mesh. 44 micron is what is recommended for work with a .018 inch nozzle size.

I use the baked 120 mesh dolomite when I am using a .025 or .040 nozzle size. Works really well for initial prep after having used an air scribe to get rid of most of the matrix , best to do final fine detail work with the .018 inch nozzle size and smaller particle size of 200 or 320. The smaller the particle the less chance of pitting your fossil. Impact force is a function of the speed the particle is travelling and its weight (PSI and nozzle size influence the speed of the particle). Also a factor is its shape of the particle. Fresh material cuts better because it has sharper non rounded edges. Re-used material gets rounded and eventually does a lesser job of cutting the matrix. I find myself always tweeking my abrasion material to get just the right cutting mix for a particular fossil (fresh dolomite, used abasive, aluminum oxide, baking soda.

For the fossils we find in Ontario shale and limestone I never mix in more than 10% aluminum oxide and I only do this for particularly hard material .

Hope this helps

Edited April 17, 2012 by Malcolmt

[TOM BUCKLEY]

Any reccomendations for a type of pan to use to "bake" my dolomite powder. Just got a fresh load in the mail today but both containers are pretty moist and they are having trouble blasting. Would glass be fine?

I am not a bake ware expert.....but if you want to use glass, stick with PYREX. I think any metal pans that are designed for baking would work fine. You can even buy the disposable foil pans in the supermarket.

Tom

[squalicorax]

Thanks guys just what I needed. Probably going to go with pyrex spread out thin. I am enjoying the low psi paasche unit, rarely burn a hole

[dragonsfly]

The shop-vac can be mounted outside or in an adjacent room (hoses are wonderful things). A switch can be mounted on the cord. I would recommend the "Fine Dust"t bag if used indoors...or... run a hose outside off the exhaust..

[Blastoid]

I bought the 1 quart stand-alone powder reservoir Paasche unit on sale at Amazon, only to find myself back here reading that the thing's no good for shooting baking soda, only the heavier faster cutting powders... and I'm into prepping Green River fish and Arkona Shale specimens, which need a light touch. Could it be modified in any way, or is it going to be useless for my purposes? Did Paasche give a reason the cannister won't work with light, fine abrasive media??? Many thanks for any help. I've got fish plates stacking up, ready for final prep, really don't want to have to finish them off with the old tungsten carbide needle lol.

B

[Malcolmt]

Pretty much all you can try is mixing in 5 to 10% aluminum oxide and running the PSI a bit higher than normal. I have 3 of the small pashe units and I general ran them at 35 PSI but would go as high as 55 with BS giving very good results (as long as the BS was totally dry). I would think that if you ran it full open and made sure that the Baking soda was totally dry (do the bake thing in the oven) that you might be able to get it to work. Try filling the canister to different levels. My small units always worked best in the top third of the canister

Since I do not have the remote canister unit this is all just a guess. You could also try dolomite. It is not as blocky as the BS

[Malcolmt]

Blastoid . Are you prepping split layer or 18 inch layer fish. For me abrasion worked great on the 18 inch layer fish and not so great on the split layer. My 18 inch layer fish are in extremely hard matrix that needs an airscribe to work effectively with it. The bone is jet black and hard as well. The split layer however is a different story. I suspect different quarries have very different characteristics based on what I have seen. the quarry I got most of my split layer (about 20 slabs) (Tinsky's) were vey flakey and needed vinac to staybalize. I have other split layer from unkown locations that seems to be less deteriorated. The matrix definately smells of oil.The vetebrae on the knightia were extremely crumbly.

[Blastoid]

All my fish are 18" layer, and all but a few are superbly preserved. The few that are really easy to prep, from a bit of weathering or whatever, do have some flaking issues, but I've not yet had to use more than a few specks of crazy glue. Are you coating your fish when done? This is something I've been wondering about for a long time, need to get some Vinac or B76.

Thanks for the info on the air abrasive unit; I've almost got everything up and ready to go. I'm feeling rather self-satisfied having finally figured out what it takes to get the air scribe to run happily, next challenge is tweaking the air abrasive.

Cheers,

B

[Malcolmt]

I use very dilute vinac pretty much painted over the entire split layer fish as the ones I have would disintegrate to nothing if just left alone. The lowest powder setting on my Comco unit at 35 PSI with the finest 44 micron dolomite pretty much obliterates the split layer fish if I try to use it. For the most part I stick to a pin vice and the scope for the split layer ones that I have. There is however a very good demarkation between matrix and fossil so they to prep decently. My ARO scribe is too powerful for close work on these. Thinking about getting a Paleotools micro jack at some point.

On the 18 inch layer I have only used vinac on spots that needed pieces reattached. My 18 inch layer (1 mioplosus, 2 priscacara, 3 diplomystus) (all are in the 10 to 12 inch size range) are very well preserved in a super hard matrix and do not seem to need any consolidation. The bone is jet black and pretty much as hard as the matrix. Unfortunately the heads on 2 of the diplos were exploded. The jury is still out on the third.

I have also heard of people coating the split layer fish with flat matte clear Krylon. It is sold in aerosols up here . I have tried it on hash plates but not split layer fish. Have not decided yet if I like it but at least it is not shiny. I do not like shiny matrix. I would not spray it , but would spray some out into a container and tthen paint it on exactly where I want it.

[Blastoid]

Very interesting about the power of the comco unit; I've been lusting for one for years now. I have a cheap clone of the ARO scribe, it really does a great job with the 18" layer fish, can get to with a few varves of the bones, then pin vise and eventually air. Lotsa fun, great way to pass the time until decent weather arrives and I can get out and catch real fish!

Cheers,

B

[TOM BUCKLEY]

I was reading the earlier messages to this string. Badger makes a similar air abrader to Paashe. It is easy to handle, refill, clean, tear down and replace parts. I don't use Baking Soda, Powdered Limestone, Powdered Dolostone, Dolomite, Aluminum Oxide, Silicon Carbide. I only use ATH (Aluminum Trihydrate). I've been telling fellow prep-parers for years. I guess it is hard to move outside the realm of familiarity. Here are some bugs that I prepped using only a pin vise and a Badger air abrader at 45 psi filed with ATH. You judge if it works.

Outstanding results!!!!

I too use ATH. Anywhere from 40 - 90 microns at pressures of 30 - 70 psi. The higher the pressure and the larger the particle size, the more aggressive the cutting action. Since I learned of it......it's all I use. My avatar is of a Phacops rana eye done with ATH.

Recently a friend sent me some specimens embedded in limestone. I'll have to break out the dolomite for them.

Incidentally, the ATH worked fine in the Paasche as well as in the Vanimen.

Tom

[Malcolmt]

No denying the results you are getting. I have always shied away from aluminum based products because it has been linked with Alzhemiers and unfortunately that seems to run in my mothers side of the family. She is now 97 and has no clue about anything......her sisters and her mother also had it.

Intersting AL(OH)3 has a hardness of 2.5 to 3.5 putting it in about the same cutting class as dolomite or baking soda. No where near as hard as aluminum oxide. The data sheet indicates relatively safe can cause lung and throat irritation. Used in some antiacid preparations.

Edited April 23, 2012 by Malcolmt

[squalicorax]

What is the speed in comparsion to dolomite of the ATH in terms of prepping shale from the devonian or ny or the waldron to a limestone encased trilobite. Id like to know if it makes much a difference between the two materials.

[TOM BUCKLEY]

What is the speed in comparsion to dolomite of the ATH in terms of prepping shale from the devonian or ny or the waldron to a limestone encased trilobite. Id like to know if it makes much a difference between the two materials.

ATH is 3.0 Mohs and dolomite is 3.5 - 4. The Mohs scale of hardness is the best indicator of how aggressive an abrasive is. Other factors are the shape of the particle, amount of abrasive in the air stream, and the air pressure used.

Tom

[Malcolmt]

Heat above 205 centigrade causes Al(OH)₃ to irreversably release its water content and become Alumina ???

Al(OH)₃ plus heat = Al₂O₃ - 3H₂0.

This is why it is used as a fire retardent as it is an endothermic reaction and produces water vapour.

As for Dolomite according to the fact sheet I got with my 44 micron dolomite from Paleotools it has a Mohs of 3.5. I know it can vary by manufacturer depending on the ratio of calcium carbonate to Magnesium carbonate in the dolomite and any impurities it might have.

I am definately going to try a small container of ATH if I can find a supplier up here in Canada.

Edited April 23, 2012 by Malcolmt

[cojo]

I was reading the earlier messages to this string. Badger makes a similar air abrader to Paashe. It is easy to handle, refill, clean, tear down and replace parts. I don't use Baking Soda, Powdered Limestone, Powdered Dolostone, Dolomite, Aluminum Oxide, Silicon Carbide. I only use ATH (Aluminum Trihydrate). I've been telling fellow prep-parers for years. I guess it is hard to move outside the realm of familiarity. Here are some bugs that I prepped using only a pin vise and a Badger air abrader at 45 psi filed with ATH. You judge if it works.

Fossilcrazy,

I'm extremely impressed with the results in your pictures. What blaster were you using?? I'm looking at picking up the paasche aec as it seems to be quite a popular one, but i thought i'd see what you were using. I wouldnt mind spending a little extra money at first to get it right in the end.

[Malcolmt]

I am not sure he said what he was using but he did make mention of the Badger which is similar to the Paasche. Note that people have been having issues with the Paasche with the remote container as it is really only meant to use aluminum oxide which on its own is too harsh for most fossils.

[cojo]

I am not sure he said what he was using but he did make mention of the Badger which is similar to the Paasche. Note that people have been having issues with the Paasche with the remote container as it is really only meant to use aluminum oxide which on its own is too harsh for most fossils.

I heard that. That's why I've been really open to something else. I've been mostly working small trilobites out of the house/weeks formation in Utah and the paleo-tools airscribe I've been using is obviously quite overkill. Any idea what model badger has been working best. I love the prep lab by the way. I'll probably set one up one following your model in the near future .

[cojo]

i think i would get by alright without the remote container. Thanks a ton for the reminder though. The more I compare the 2 the more I lean toward the paasche although the container is a bit smaller. With the small trilos i'm doing it shouldn't take too much abrasion media and I don't mind refilling a few times. I do think i'd try to rig a syringe tip to the end to be a little more precise too.

[Malcolmt]

I owned 3 of the Paashe, eventually the brass orfice that has tiny holes in it at the bottom of the container gets the holes worn out and the adjusting screw at the top of the container gets destroyed and becomes immobile. But for the price you will likely get a 100 hours blasting from a Paasche. So it is a very inexpensive way to start air abrasion and the results are as good as seen here . Here is a phacops that was prepped with the Paasche

You definately need to build a blast cabinet and do something to filter the dust or you will be sorry.

I found the 22 gage dispensing tip(not sharp) to be the most usable with the Paasche. The pasche works fine with dolomite or baking soda in the 100 to 200 mesh range. At less than 100 mesh it will clog up but is easy to clear, just unscrew te nozzel and blow it out. I would set the flow as low as possible and use at 35 PSI. You need to use dry abrasive because the Paasche works by blowing the air up into a cloud that then gets pulled out the nozzel with the airflow. Tends to clump if it gets mositure. (Your compressor will put mositure into the media)

Edited April 24, 2012 by Malcolmt