Aluminum Trihydrate (My Tests On It)

[Malcolmt]

Well I finally managed to acquire 5 kilograms of aluminum tri hydrate Al(OH)₃ with 100% guaranteed to be smaller than 200 mesh and 90% guaranteed to pass through a 300 mesh screen. The tests I ran were as is; unscreened out of the bag. The tests were using a COMCO air abrasion unit at varying presures from 2 PSI to 90 PSI. I paid $35 for 5 kilograms (about 11 pounds). The material seems to be very consistant in size definately under 50 microns. A small particle size is good for delicate prep work.

The data sheet that came with the product rates it as non hazardous which is a very good thing , regardless I always wear a mask and operate in a negative pressure blast cabinet. The material I got appears to be pure with 0% silicates according to the data sheet.Silicates are a bad thing. Nasty to breath and tough on fossils

Let me state that overall I was disappointed for the type of work that I am generally doing. I had heard so many good things about this media on the forum here.

So what did it do well. It was an excellent media for cleaning Penn Dixie trilobites . It appears to be harder than the matrix but softer than the actual trilobite. I would give it a 10 out of 10 for cleaning fossils from the Windom formation. The trilobite practically cleans itself.

It did very well at low pressure 2 to 10 PSI with a small nozzel (.018) cleaning black shale from New York state that contains triarthus and another sample from Ontario containing psuedogygites. At higher pressure (40 to 60 PSI and a larger nozzel (.025) it cuts through the shale like butter, works good on delicate shale comparable to the results I get from pure calcium carbonate.

Veralum formation grey matrix, James Dick Quarry Brechin, Ontario. Does a good job removing grey matrix seems reasonably gentle on tan coloured flexicalymene trilos. However will not remove at all the tan matrix that is found at the very top of the quarry that you can find crinoid stems in. Dolomite will remove this tan colored matrix albeit slowly.

Whitby formation, St. Mary's cement quarry Bowmanville Ontario. Cuts through matrix slowly but does not appear to cut the isotelus trilobite at all. Looks like will be an excellent abrasive for material from this quarry . Ran test at 60 PSI. Needed a bit higher PSI to take matrix off at an acceptable speed.

Harrigan Formation trilobites Clarita, Oklahoma (tan coloured). Cuts through matrix very easily. A bit more forgiving on actual caramel coloured trilobites and shells than dolomite.

Arkona, Ontario .... Widder, Hungry hollow and Arkona formation trilobites works ok but not as well as the 44 micron dolomite that I normally use on these. For a fragile trilobite it may be preferencial to the dolomite as it does not cut quite as well. But it is much slower in the 30 to 40 PSI range which I generally use on these trilos.

Waldron Shale worked very well semes to be harder than the matrix but softer than the typical caramel colored trilobite. would rate it a 8 out of 10 , does not cut the matrix as well as dolomite but seems more forgiving on the actual trilobite.

Heres the bad news for me . It will not touch the Moroccan trilobites in the dark grey matrix or the tan matrix . Tried tests on material from 3 different localities. The matrix is definately harder than the aluminum trihydrate (3.0 on the Mohs scale). Even as high as 95 PSI observing under high magnification their was no noticeable abrasion. Dolomite at a Mohs hardness of 3.5 will work on this matrix though it is by no means a speedy process.

I will try to update this post with some tests on samples from other localities as I get a chance.

Edited January 24, 2013 by Malcolmt

[AgrilusHunter]

Hi Malcolm,

Absolutely great post! I'm just learning air abrasion so reviews and other people's experiences are big for me. This kind of review is why I love this forum. Thank you!

[Nandomas]

Thanks for this post. I am learning a lot here

Just to be accurate, are you speaking about the flame retardant Alumia tryhidrate ? and, more important, did you notice difference with regular aluminium oxide?

Edited January 23, 2013 by Nandomas

[Malcolmt]

I believe that it is used as a flame retardant. The formula is Al(OH)₃

There is no comparison between this and aluminum oxide. Pure aluminum oxide cuts through all fossils like butter. Using aluminum oxide is a quick way to destroy a fossil unless you are an expert with very high end equipment.

Some will mix in up to 10% aluminum oxide into baking soda or dolomite to get an abrasive that cuts a little bit better. I do not do this.

I do not use aluminum oxide as it is far to abrasive for the type of fossil preparation that I do. The alumina trihydrate has a Mohs hardness of 3. This is slightly less than dolomite that averages at about 3.5. Aluminum oxide is super hard at 9. Chalk ( calcium carbonate) is rated at 3 and sodium bicarbonate (baking soda) is rated at 2.5. Talc which we all think of as super soft is rated at 1. Diamond at the top end of the scale is rated 10.

[jpc]

malcomt-

great post. I wonder how it owuld work on the stuff I collect. Where did you get the Al(OH)3? Thanks for telling us about this.

Yes, nando... aluminum oxide is very different, and as malcomt says, it will eat your fossils. Avoid it 99% to 100% of the time.

[Fossildude19]

malcomt-

great post. I wonder how it owuld work on the stuff I collect. Where did you get the Al(OH)3? Thanks for telling us about this.

Yes, nando... aluminum oxide is very different, and as malcomt says, it will eat your fossils. Avoid it 99% to 100% of the time.

JPC,

I noticed that they sell it on the Axner website.

It is listed as Alumina hydrate, but I believe it is the same thing.

Regards,

[Malcolmt]

Alumina Hydrate is just another name for Aluminum trihydrate. I got the bag at a very large pottery wholesaler up here in Canada that specializes in making custom glazes. If it is used for potter they pretty much had it. I went there in person and checked out the particle size and data sheets before buying. Also got some dolomite and calcium carbonate from them to try. They sell those dirt cheap < $20 for 44 pounds. (I bought 5 kilogram bags just to try.)

[Nandomas]

just to be sure before order a bag to give a try...

is this one?

http://en.wikipedia.org/wiki/Aluminium_hydroxide

Thanks for your time

Nando

[Fossildude19]

I have ordered 5# bags of Alumina Hydrate (Aluminum Tryhydrate), Dolomite, and Calcium Carbonate from Axner. I'll see how things go with these mediums and report back here.

So far, I have only used baking soda (sodium bicarbonate) purchased from the grocery store - works okay so far, been a bit cold for the fossil shed of late.

Regards,

[Malcolmt]

Nando,yes that is the same material that is called aluminum trihydrate. Goes by a lot of different names depending on who is selling it. some just call it alumina.

[Lmshoemaker]

Which would you recommend more, the alumina trihydrate, or dolomite?

[Malcolmt]

No good reason but I think for the material that I prep my preference is dolomite. I am also (for no scientific reason) a bit gunshy of anything that I don't really know how dangerous it is. I am just cautious of anything that has aluminum in it as aluminum has been linked to alzheimers. The data sheets say that it is safe. Personally it was not different enough from 40 micron dolomite to really warrant me using it.

[Lmshoemaker]

Thanks Malcolm!