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Doctor Mud

Tumido Prep Number 3

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Doctor Mud

Time to start crab number 3. The first one was a "starter crab" incomplete but good to practice on. The second was a big sucker - finally got the proper tools towards the end. Took over 200 hours using engravers - never again!

Engravers do nowhere near the same job as the ME-9100 and microjack. The rock just doesn't flake offf as well. Particularly for bulk matrix removal.

I spotted this concretion and no evidence for a crab was there. No legs. So I split it open

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It's about 30 cm across. So quite a large concretion for this locality. Looks like all the legs are there, right to the tips. Yay!

I then glued and clamped after supergluing in any frags that had fallen off.

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I used a 2 part epoxy to give me time to work.

I then scribed a score mark and got to work with the chisel. This is the best way to remove bulk matrix if you don't have a mighty-jack or similar larger air chisel.

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I could tell where I might encounter crab since I had a preview via the split. Got to allow that the legs might be on weird angles and I stopped when I saw the tip of a leg, and then scribed a "window" down to the top of the carapace. You can just see it in the middle. Luckily in this concretion the rock starts to change colour just before the shell - goes a rusty orange.

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Here's where I am at now. Exposed the hind end - articulation of the hind legs and started to work out where the hind legs go. Next to expose the rest of the legs and the front - the two pincers.

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The only issue with this crab is that the carapace is very fragile at the front end, a thin (< 1mm) layer of the darker brown shell peels off. I found this on my previous crab, the rest of the shell is robust and the matrix flakes off easy - with the ME-9100. Just around one particular area on the front end in an area about the size of a nickel where the distinctive patterning tends to be. Last time I just had to go easy with a low setting on the Microjack. I guess this is where an air abraider would come in handy. You can see I've left the matrix on there for now.

I've left that bit for later at the start of a session when I'm fresh - also might skip the coffee before that session!.

Stay tuned - more work this week after a Sunday break.

Edited by Doctor Mud

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fossisle

Wow that one looks great , keep up the good work

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Ludwigia

Oh Goody! Another crab prepp!!! Lookin good!

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Raggedy Man

Wonderful work Doctor!

Hey ... wait a second lol.

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RJB

Cool to see other folks prep crabs!!! Good job mud dr.

RB

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sseth

Great work. Looking good

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Doctor Mud

post-11936-0-05949500-1418803351_thumb.jpg

More progress.

8 out of 10 appendages located - 2 legs still to be found. Could be behind the others.

I've been using the ME-9100 for bulk matrix removal and the Microjack #6 for close up work.

The thing that really takes time with these large concretions is the hardness of the rock and the sheer amount that has to be removed.

Next I'm going to approach the front to expose the front of the carapace and the pincers. Then I'll work my way out to find the tips of all the legs - and hopefully the missing two.

Finally, I'll work making sharp rock, shell transitions, smoothing the matrix etc. to improve contrast.

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RJB

Its lookin DANG good so far!!!

RB

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Kosmoceras

Looks like this is going to be a good one! :D :D

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Ludwigia

Nice work! Getting the eyes free is going to be tricky isn't it!

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Doctor Mud

Thanks guys!

Ill try not to jinx myself as anything can happen.

Hoping for the best for the front end and legs. So far the shell is mostly nice and dark brown so the rock flakes away nicely without too many dramas.

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Doctor Mud

Nice work! Getting the eyes free is going to be tricky isn't it!

Yes - it has been a low process since the claws are so close. I've figured out where they go and the next step will be to slowly work down until the eyes are exposed.

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Doctor Mud

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Getting there. Most things are exposed. Check out that leg! I haven't found the end yet. I hope the rest are like that. I know that two on the other side are.

Next I will remove a lot of matrix from the front to make it easier to get at the front. I'll leave the rest of the claws and eyes till last - to protect them from damage.

Still a diamond in the rough. Lots of work to really make the legs pop. Sharpen the shell/rock transition and remove any traces of rock. An air abraider would be great for this. You can see the tricky bit wherer the shell was a little delicate. A bit of stop 'n' glue prepping was required. A huge relief to get past that and into nice dark brown shell again.

Unfortunately, no more posts on this one for a month. I'm off to New Zealand for Christmas. I'll be making another trip to the tumido site and hope to pick up a couple of concretions. I spotted some huge concretions (50 cm plus across) and I'm going to try and split one or two.

Happy holidays to all TFF members. I hope you all have a great time with your family and I look forward to hearing about everyones holiday fossil adventures - in the field or in the prep lab.

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Auspex

Have a terrific Holiday; we'll keep the light on for you :)

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Ludwigia

This is looking more promising all the time!

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Doctor Mud

Have a terrific Holiday; we'll keep the light on for you :)

Thanks Auspex! I'm in New Zealand now. I'll still be on now and then, but mostly eating drinking, fossiling and being merry....not necessarily all at once :P

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Renmanart

That's coming along beautifully.

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Doctor Mud

Thanks Renmanart.

I'm going to get back into this soon.

RB has inspired me with his awesome tumido posts.

I've been working on a new work bench/cubicle and the last coat of varnish is now drying.

Can't wait to get back into it!

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RJB

I love the legs on this one! I hope you get a couple more coming out toward the front? That would be super! Do you have the missing part of that right claw finger? an easy fix if you don't. Looking forward to seeing this baby done! Wooooop! Woooooop!

RB

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Doctor Mud

Thanks RB.

This one sure does have some complete legs! Got lucky on a day when I walked for ages and it was my last day before getting on a plane. I thought that looks like a suspicious looking concretion. No sign of exposed legs so I split it open.

The right (large) claw is complete (see the first image). It's going to be tricky as the rock fractured leaving a thin coating of matrix. Looks like a perfect job for an air abraded or perhaps a delicate tickling with a micro jack since I don't have an abrader.

You can't see it all in the last image as I haven't removed all of the rock yet. Once the bulk of the rock is removed ill be left with the original fracture surface on top of the right hand claw. I didn't stick adhesive on that part when I glued the concretion back together.

Once I get to that part ill post a clearer image so you know what I mean.

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Doctor Mud

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Latest update.

Found all but one leg. One is hiding behind the others on the right hand side. No idea where the leg is on the left....

Not sure whether to keep digging and look for it or not.

You cant see it in this view, but I have one eye exposed on the right.

Next I'll continue to work on the front exposing the claws and other eye, then smooth the matrix out some more.

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fossilized6s

Great job so far Doctor Mud! Beautiful crab.

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Doctor Mud

Thanks!

Almost there. Found the last leg. It points out to the front left in between the left claw and the leg visible in the last pic.

And it goes right to the tip.

I was removing matrix and got lucky. And to think I wasn't going to carry this crab out!

Sorry - no update pic but ill fix that soon.

Also solved the "problem" of the very thin (< 1 mm) layer of rock left on the big pincer on the fracture surface.

All I needed was a magnifying visor (full magnification) micro-jack set way down low, and a steady hand.

Once I got started and had a clean rock/shell interface patience was all that was required.

I guess it was just like removing the thin layer of calcite that sometimes adorns these guys.

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RJB

So nice to see soooooooo much leg, and happy for you that you found the last one. Great job Doctor Mud!

RB

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Wrangellian

Wonderful job! It's miraculous to me how anyone can expose a delicate fossil within a big hard rock, but I'm glad to see it can be done. I just wish some of the ammo preppers could be as careful...

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