How to choose abrasive media?

[Cowboy Paleontologist]

Hello!

I have recently acquired an air eraser to prep fossils out with, and I was just wondering how to choose an appropriate abrasive for the task.  I have a few different items I would like to prep out, but most specifically are some horn corals and hexagonaria from the Devonian Coralville formation.

[Kane]

1 minute ago, Cowboy Paleontologist said:

Hello!

I have recently acquired an air eraser to prep fossils out with, and I was just wondering how to choose an appropriate abrasive for the task.  I have a few different items I would like to prep out, but most specifically are some horn corals and hexagonaria from the Devonian Coralville formation.

I would go with dolomite at 40 micron size for limestone or denser shales, and baking soda for fine details and more delicate pieces.

[Cowboy Paleontologist]

Thanks!  

Would you recommend these two for pretty much all uses?  Like if I wanted to prep out some Green River fish or something.

 

[Kane]

4 minutes ago, Cowboy Paleontologist said:

Thanks!  

Would you recommend these two for pretty much all uses?  Like if I wanted to prep out some Green River fish or something.

 

Much harder matrix might require more heavier duty abrasive medium. In terms of GR fish, I've read that it is better done by hand using an X-acto blade. 

 

For my purposes, I rely exclusively on dolomite or baking soda, but nearly all my work is on trilobites in shale.

[Sagebrush Steve]

3 hours ago, Kane said:

Much harder matrix might require more heavier duty abrasive medium. In terms of GR fish, I've read that it is better done by hand using an X-acto blade. 

 

For my purposes, I rely exclusively on dolomite or baking soda, but nearly all my work is on trilobites in shale.

You are depressing me.  I’m prepping several Green River fish from the 18” layer right now by hand using needle probes and have been thinking, “there’s got to be a better way.”  I have been looking into getting an air eraser and loading it up with dolomite.  But if you’re telling me I’m already doing it the best way then I will struggle on.  Or were you referring to fish from the split fish (aka “sandwich”) layer?  I can understand you wouldn’t want to touch those even with baking soda.

[Kane]

2 minutes ago, Sagebrush Steve said:

You are depressing me.  I’m prepping several Green River fish from the 18” layer right now by hand using needle probes and have been thinking, “there’s got to be a better way.”  I have been looking into getting an air eraser and loading it up with dolomite.  But if you’re telling me I’m already doing it the best way then I will struggle on.  Or were you referring to fish from the split fish (aka “sandwich”) layer?  I can understand you wouldn’t want to touch those even with baking soda.

This is only what I've read here, and I think it pertains to the "sandwich layer" fish. I know @Ptychodus04 has worked on his fair share of fishies, so hopefully he sees this and can give you much better advice than I can!

[Ptychodus04]

1 hour ago, Kane said:

This is only what I've read here, and I think it pertains to the "sandwich layer" fish. I know @Ptychodus04 has worked on his fair share of fishies, so hopefully he sees this and can give you much better advice than I can!

Consider this seen and I’ve never been accused of keeping my opinions to myself.

 

For sandwich/split fish material, I remove bulk matrix with my CP9360 then switch to the Micro Jack 4 under a microscope for prepping the fish itself. Anything larger and the fish will disintegrate. I heavily consolidate as bones are exposed. Never use abrasive on these fish. Even the discharge air from an Aro will blow the fish apart.

 

For 18” stuff, I prep with the CP and Aro if larger in size and Aro/Micro Jack if smaller to get down to the fish. Once I have most of the bones exposed and the fish totally outlined, I use baking soda at a relatively high pressure (upwards of 90 PSI) to remove the remaining matrix. 

 

If your abrasive system can’t handle the higher pressures, you have to use a harder abrasive. I find the softer abrasive at higher velocity to be more forgiving and quite productive.

[Sagebrush Steve]

2 hours ago, Ptychodus04 said:

Consider this seen and I’ve never been accused of keeping my opinions to myself.

 

For sandwich/split fish material, I remove bulk matrix with my CP9360 then switch to the Micro Jack 4 under a microscope for prepping the fish itself. Anything larger and the fish will disintegrate. I heavily consolidate as bones are exposed. Never use abrasive on these fish. Even the discharge air from an Aro will blow the fish apart.

 

For 18” stuff, I prep with the CP and Aro if larger in size and Aro/Micro Jack if smaller to get down to the fish. Once I have most of the bones exposed and the fish totally outlined, I use baking soda at a relatively high pressure (upwards of 90 PSI) to remove the remaining matrix. 

 

If your abrasive system can’t handle the higher pressures, you have to use a harder abrasive. I find the softer abrasive at higher velocity to be more forgiving and quite productive.

That’s good to hear, thanks.  I thought I recall you saying you use the Paasche AECR eraser with the external tank, but I must be wrong because that one won’t tolerate anything above 50 psi.

[Ptychodus04]

On 7/3/2018 at 5:08 PM, Sagebrush Steve said:

That’s good to hear, thanks.  I thought I recall you saying you use the Paasche AECR eraser with the external tank, but I must be wrong because that one won’t tolerate anything above 50 psi.

I use one made by Cyclone Manufacturing. It was originally developed for use on jewelry.