Dipping my toe in to micro air abrasion prep with a tricky fossil crab

[mamlambo]

I've got some experience with air scribes and acid (acetic) but haven't used air abrasion much. I recently got a new micro air abrasion unit and tried it out on a sticky crab that had a growth on it with some good results using dolomite.


Before photo:




After photo (work in progress, about 25 of prep time):

 

 

One of the challenges I have is that is it really hard to find media between 50 and 100 microns here in New Zealand and shipping is quite expensive. I can sift my own dolomite, it just takes ages! I wonder if anyone has any tips for finding iron powder or is there an easy way to make your own?

Here's a video of the unit I am using as well as my setup, any help / suggestions welcomed! 

 

[RJB]

Oh boy!  I've seen a heck of a lot of Tumido's but never one with this "stuff" on it.  Quite interesting.  By any chance do you know what the growth is?  And I never would have dreamed that one could use Dolomite in a crab and not leave those god awful wave patterns on it?  I wish I could help you out with where to get 50 micron dolo, but have no idea in NZ.  Best of luck to ya with that. 

 

RB

[jpc]

Have you tried pottery supply places in NZ for dolomite?  That is where I get mine.  You still have to sift it but it sifts pretty quickly.  NIce crab.

 

 

[caterpillar]

I am not convinced of the use of a micro sandblaster to prepare crabs. It's too abrasive.

We can clearly see the result on the shell and especially the claws of this crab.

This crab was fossilized with pyrite (the ribs are visible). They can never disappear.

The use of a deflocculant would have made it possible to remove the excess matrix without attacking the fossil.

But in any case, these ribs are the particularity of this crab

[mamlambo]

1 hour ago, caterpillar said:

I am not convinced of the use of a micro sandblaster to prepare crabs. It's too abrasive.

We can clearly see the result on the shell and especially the claws of this crab.

This crab was fossilized with pyrite (the ribs are visible). They can never disappear.

The use of a deflocculant would have made it possible to remove the excess matrix without attacking the fossil.

But in any case, these ribs are the particularity of this crab

Thanks for the reply! Can you perhaps circle the damage on the shell and claw photos? I'm still starting out with the air abrasive so would love to learn.

Also, what do you mean when you refer to "ribs"?

[mamlambo]

7 hours ago, RJB said:

Oh boy!  I've seen a heck of a lot of Tumido's but never one with this "stuff" on it.  Quite interesting.  By any chance do you know what the growth is?  And I never would have dreamed that one could use Dolomite in a crab and not leave those god awful wave patterns on it?  I wish I could help you out with where to get 50 micron dolo, but have no idea in NZ.  Best of luck to ya with that. 

 

RB

I don't know what I don't know yet when it comes to air abrasion, I'm glad I didn't know about the wave patterns! I have no idea what the growth is, the matrix is also much softer than I am used to. I'll make another post and ask for an ID on the growth on the crab. I'm not sure if it's animal or mineral 

[hadrosauridae]

I absolutely hate dolomite.  I tried it briefly, and it makes such a huge mess I gave it up.  Its a shame, because it did a great job where I used it.  Bicarb work well for most of my preps, and I just started working with iron in place of the dolomite powder.  MAB is such a wonderful final prep tool.  Good luck and hope you find your source of iron powder!

[jpc]

5 hours ago, hadrosauridae said:

I absolutely hate dolomite.  I tried it briefly, and it makes such a huge mess I gave it up.  Its a shame, because it did a great job where I used it.  Bicarb work well for most of my preps, and I just started working with iron in place of the dolomite powder.  MAB is such a wonderful final prep tool.  Good luck and hope you find your source of iron powder!

MAB?

On the other hand... I like dolomite for the right projects.  Bones in limey concretions for example... the same as these Tumicodarcinus crabs are in.  Bicarb doesn't touch it.

[hadrosauridae]

2 hours ago, jpc said:

MAB?

On the other hand... I like dolomite for the right projects.  Bones in limey concretions for example... the same as these Tumicodarcinus crabs are in.  Bicarb doesn't touch it.

Micro Air aBrasion?  

 

I agree, I have echinoids that bicarb wont touch the matrix on, and dolomite did a great job, but its just so much of a pain.  Thats why I'm trying iron powder.  Decent results so far, little mess.  I'm tempted to mix a little dolo into the iron.

[caterpillar]

14 hours ago, mamlambo said:

Thanks for the reply! Can you perhaps circle the damage on the shell and claw photos? I'm still starting out with the air abrasive so would love to learn.

Also, what do you mean when you refer to "ribs"?

 

There is not a particular place where you see the abrasion. We see that the surface of the crab has been slightly polished. The cuticle of crustaceans is very fragile and the preparation with the sandblaster destroys it. But maybe by using baking soda the result would be appreciable.

The word "rib" is not suitable. I let you talk about the surface veins.

It's just my humble opinion because I know you have a lot of experience in preparing crabs

[mamlambo]

9 hours ago, caterpillar said:

 

There is not a particular place where you see the abrasion. We see that the surface of the crab has been slightly polished. The cuticle of crustaceans is very fragile and the preparation with the sandblaster destroys it. But maybe by using baking soda the result would be appreciable.

The word "rib" is not suitable. I let you talk about the surface veins.

It's just my humble opinion because I know you have a lot of experience in preparing crabs

Thanks! I appreciate you pointing this out!