Removing paster jacket?

[abctriplets]

Ok, I am a novice to this whole fossil-prep thing....

 

So we found a couple of large (well, for us) bones in the field, and as they were starting to fragment a bit, we put a thin plaster jacket around it, and dug under the dirt to remove the blob, and packed the whole thing in foil.

 

Back home, I flipped the chunk upside down, and removed the dirt and prepped the bottom of the bone.

 

So now I have to do the top side...any tips on the next step? Am I over-thinking this, and the plaster hasn't bonded to the bone?

[aerogrower]

Did you put anything between the plaster and the fossil. Wait for experts but that might be a problem.

Edited August 2, 2017 by aerogrower
I can't spell

[abctriplets]

I actually wasn't fully watching that step. In retrospect, wouldn't Vaseline be good? We were using a PVA bonding solution earlier. But yeah, not sure if the plaster went directly on the bone or not....

[Ptychodus04]

If the plaster is directly on the bone, it's probably there for eternity. If there's a separator, you should be able to peel the jacket away from the bone at the edges. Post a couple pics of the edge of the jacket.

 

Typically, toilet paper, paper towel, or foil is used as the separator. All you are doing is creating a physical barrier between the bone and the jacket.

 

If the bone is extremely brittle and degraded, plaster can be poured directly on the bone with the intent for the plaster to soak in and remain on the bone to provide support with the under side being the only part prepared.

[abctriplets]

Yeah, my wife says our guide just put the plaster strips right on the bone. Sigh.

[Ptychodus04]

8 hours ago, abctriplets said:

Yeah, my wife says our guide just put the plaster strips right on the bone. Sigh.

 

That is either because the bone is so degraded that the only option for it to be collected was permanent plastering or it is because your guide doesn't fully understand the process of applying a field jacket.

 

I tend to be a bit in the cynical side (I've been told; I say I'm more of a realist) so I lean towards option B. I have collected some seriously degraded bones that were happy without plaster in them. We are taking about so degraded that the were described as looking "like the were eaten by a coyote and s$&t off a cliff." 

 

Your knot option now, other than leaving them as they are, is to consolidate the bone with the PVA and attempt a mechanical removal of the jacket.

 

This is a royal pain but you can get the jacket wet and chip away bits of plaster until you can pull the burlap off. Than continue carefully chipping the plaster off the bone. You'll have to go after the bits of plaster in the pores with a needle.

[jpc]

17 hours ago, abctriplets said:

Yeah, my wife says our guide just put the plaster strips right on the bone. Sigh.

I hate to say bad things about people online, but that is NOT a dinosaur guide.  Find someone else to go with.  This is so incredibly amateur, I can't believe someone is doing this.  Always use a separator between bones and plaster.  And, no, not Vaseline, or you will have oily bones forever.  TP, paper towels, newspaper or alum foil.  Rant over.  I am calming down. (I am also leaning on ptych's Option B).

 

If you are lucky, the plaster can be sandblasted off.  If you are unlucky... see ptych's comment about soaking in.    

 

Can you post pix of this project for more advice?

[abctriplets]

15 hours ago, Ptychodus04 said:

 

This is a royal pain but you can get the jacket wet and chip away bits of plaster until you can pull the burlap off. Than continue carefully chipping the plaster off the bone. You'll have to go after the bits of plaster in the pores with a needle.

 

Thanks. This has been my day today....

[abctriplets]

7 hours ago, jpc said:

I hate to say bad things about people online, but that is NOT a dinosaur guide.  Find someone else to go with.  This is so incredibly amateur, I can't believe someone is doing this.  Always use a separator between bones and plaster.  And, no, not Vaseline, or you will have oily bones forever.  TP, paper towels, newspaper or alum foil.  Rant over.  I am calming down. (I am also leaning on ptych's Option B).

 

If you are lucky, the plaster can be sandblasted off.  If you are unlucky... see ptych's comment about soaking in.    

 

Can you post pix of this project for more advice?

 

Yeah, this was the assistant/helper/volunteer/friend - didn't have many answer for us regarding geology or paleontology. And foil was used....as the last layer.

 

But yes, I have been wetting and chipping away at it today. Luckily it's not too huge, nor too fragile. And not that important (but to us it is). But depressingly, I have a feeling that the other large pieces found in the vicinity, and under/on, and glued back together from around it, may not actually fit directly on this piece.  I'll post a pic/thread in a day or so on the "identify me" section. 

[Ptychodus04]

9 hours ago, abctriplets said:

 

Yeah, this was the assistant/helper/volunteer/friend - didn't have many answer for us regarding geology or paleontology. And foil was used....as the last layer.

 

But yes, I have been wetting and chipping away at it today. Luckily it's not too huge, nor too fragile. And not that important (but to us it is). But depressingly, I have a feeling that the other large pieces found in the vicinity, and under/on, and glued back together from around it, may not actually fit directly on this piece.  I'll post a pic/thread in a day or so on the "identify me" section. 

 

I hope you got a discounted fee for an incompetent guide or at the very least are planning to let the owner know what happened.

[abctriplets]

Here's how it ended up.

I'm not too excited about working on the 2nd piece, as it seems a lot more delicate. But it does seem wetting the plaster, brushing with a toothbrush and pick, and wiping clean (and then sealing/gluing.....) seems to to the trick. Eventually.

 

And yes, if I can figure out a couple of ids on a few of the finds, I'll include that to have a balance of criticism & interest in an email to the owner...

Thanks again