Air abrasive on GRF Fish?

[holdinghistory]

I have heard of using an air abrasive for GRF fish, but haven't been able to find any pointers on how to do it. Is this a safe method of matrix removal? I have one slab I am working on now (first try on a fish) and have been thinking of getting some more 18 inch layer fish to prep if I can. I am guessing you would use bicarb versus dolomite. If you do use this method, any pointers on PSI, and overall technique, when to use, when not to use? So far I have just been very sporadically working on it with an Aro.

 

Nathan

[Ptychodus04]

Definitely use sodium bicarbonate. Anything harder will do bad things to your fish. Also, do not use abrasive on split fish layer stuff. They are way too soft.

 

I typically run my abrasive at around 60 psi. I know there are folks here that run much lower than that. There’s not really much advice I can give on technique other than don’t hold your blast in one spot. I keep it moving around and will come back to stubborn places a few times. If you stay on one spot, you’ll abraded the fish pretty badly.

[RJB]

Most of what Kris has just said is spot on.  There is rock with bone in it that is hard enough to be able to use strait dolomite, but with most of the fish ive been working on lately i will use a mixture of bicarb and dolomite.  Most of my fish are from the 'bottom cap'.  Those layers are just underneath the 18 inch and usually are harder and denser than the 18 inch too.  These are a bit harder to prep and the very reason a quarry owner let us dig a huge portion of it 2 years ago.  But for the 18 inch fossils and split fish fossils, I would agree whole heartedlee with Kris.

 

RB

[holdinghistory]

Thanks guys! I will have to give that a try.

[Vaniman]

Here is a recent picture-this specimen has been encased in limestone.  The pic is after about 45 minutes of sandblasting using a dolomite micro-abrasive media and an adjusted range of 20-60 psi of pressure with a Vaniman unit. Works pretty well. Hope this helps!

 

 

 

[Sagebrush Steve]

23 minutes ago, Vaniman said:

Here is a recent picture-this specimen has been encased in limestone.  The pic is after about 45 minutes of sandblasting using a dolomite micro-abrasive media and an adjusted range of 20-60 psi of pressure with a Vaniman unit. Works pretty well. Hope this helps!

 

Where is this fish from?  Looks sort of like the Green River 18” layer, but I’ve heard dolomite can be too abrasive for those specimens.  But there is nothing like a real example to use as reference.  Thanks.

[Vaniman]

Correction!! it looks like it came from a small quarry in Wyoming!  So you're right- I think it is from the Green River area. 

Edited March 14, 2018 by Vaniman
Wrong location noted

[holdinghistory]

Good to know! So you prepped that just with air abrasive, no scribe?

[Ptychodus04]

1 hour ago, holdinghistory said:

Good to know! So you prepped that just with air abrasive, no scribe?

If the fish is only covered by a thin film of matrix, abrasive is all that is really needed.

[Sagebrush Steve]

2 hours ago, Vaniman said:

Correction!! it looks like it came from a small quarry in Wyoming!  So you're right- I think it is from the Green River area. 

Looks like it might be a Knightia eocaena, a pretty common fish in the Green River beds.  Yours is a nice one, good prep job.