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Questions about preparing a crab


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TriloCrabs

I was lucky enough to find a crab concretion, and not knowing what it was, opened it with a hammer. I included images below for reference of what I am talking about.

 

* Part of the leg and claw are in imprint. What is the best approach getting them out without damage? I'm thinking manual tools?

* It looks like there might be another concretion connected to that piece. Would I be able to freeze-thaw to open it now that the other fossil is exposed or could this cause damage?

 

 

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Fossilis Willis

I would advise against trying freeze/thaw on LCF concretions. Also, it's difficult to get good results with manual/hand tools on all but the softest concs. Your best bet is glue and clamp, the work your way down to the crab very carefully with an air scribe. If you don't have these tools available, I would recommend enjoying it in its current state until you can aquire the necessary tools or enlist the help of someone with appropriate set up. All in all, not the worst outcome for a "popped" concretion. Congrats on finding it, welcome to seriously addicting hobby.

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What Fossilis Willis said.   You cannot 'freeze/thaw' these open.  Microwave does not work either.  I knew a guy who distroyed his by trying.   I can easily see that this needs to be glued back together and then prepped back down to it and even then it will still need a tad bit of repair.  Also, the chance that there is another crab on the other side is very doughtful.   But you never know.  Mother nature can at times throw in a nice surprize once in awhile.

 

RB 

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LabRatKing

All jokes about melted butter and fresh garlic greens aside, I agree with the others, an air scribe and small abrasive blaster is the best method. Even then it takes many many hours and lots of patience.

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I would like to add my agreement with FW's advice.  Nice find.  Enjoy it as is if you are limited in tools.  To do a crab well, you also need a microscope.  

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TriloCrabs
On 2/25/2021 at 12:47 AM, Fossilis Willis said:

I would advise against trying freeze/thaw on LCF concretions. Also, it's difficult to get good results with manual/hand tools on all but the softest concs. Your best bet is glue and clamp, the work your way down to the crab very carefully with an air scribe. If you don't have these tools available, I would recommend enjoying it in its current state until you can aquire the necessary tools or enlist the help of someone with appropriate set up. All in all, not the worst outcome for a "popped" concretion. Congrats on finding it, welcome to seriously addicting hobby.

 

Haha, thanks. After more reading it sounds like use a clamp or vice to 'pop' the concretions, glue the fossil pieces back together, then cut down to the fossil (using a diamond tip on dremel for example), then when you get close use an air scribe? I saw the CP9160 is $124 on Amazon, would that work? I saw a lot of air scribes are very expensive and out of my budget range.

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This would probably require lots of prepping experience, not just $124 air scribe:Wink1:

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TriloCrabs
27 minutes ago, RuMert said:

This would probably require lots of prepping experience, not just $124 air scribe:Wink1:

Gotta learn somehow. Covid isn't exactly an ideal time to learn...

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Ptychodus04
3 hours ago, TriloCrabs said:

I saw the CP9160

 The prep with this scribe will take forever. If you want to try your hand at the prep, a CP9361 or ME9100 is what you need. The 9100 is the better tool in my opinion, I’ve owned both.

 

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55 minutes ago, Ptychodus04 said:

 The prep with this scribe will take forever. If you want to try your hand at the prep, a CP9361 or ME9100 is what you need. The 9100 is the better tool in my opinion, I’ve owned both.

 

Are you sure? Judging by the carpet fibre size in the background, the specimen seems a bit small. I know I would be leery of bringing in big ME on a small piece (I've done it, but only when I'm feeling like Super Dave Osborne :P ). If it was big (RJB standard big), I'd say ME for sure! Or, if it is going to be a glue-on job to bring the halves together and prep from the top, again, definitely 9100.

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TriloCrabs
4 minutes ago, Kane said:

Are you sure? Judging by the carpet fibre size in the background, the specimen seems a bit small. I know I would be leery of bringing in big ME on a small piece (I've done it, but only when I'm feeling like Super Dave Osborne :P ). If it was big (RJB standard big), I'd say ME for sure! Or, if it is going to be a glue-on job to bring the halves together and prep from the top, again, definitely 9100.

Most of the concretions I have are under 4" in size. This one is about an inch.

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TriloCrabs
1 hour ago, Ptychodus04 said:

 The prep with this scribe will take forever. If you want to try your hand at the prep, a CP9361 or ME9100 is what you need. The 9100 is the better tool in my opinion, I’ve owned both.

 

Those are a bit out of my price range. After spending a few hours looking, I think I am going to call tomorrow and see what the price is of the All Air products 8315B and extended tip currently is. It seems a lot cheaper and able to do the job - there are posts on here saying it can handle crab matrix.

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Fossilis Willis

I bought my cp9361 from an auction site for around 70 bucks. Of course the stylus upgrade cost more than the scribe itself. I've thought about getting ahold All Air myself to see what they charge to see what they charge for a 8315 these days, I hear goog things. It's crazy to me that they don't sell them on their website, only over the phone.

7 hours ago, TriloCrabs said:

 

Haha, thanks. After more reading it sounds like use a clamp or vice to 'pop' the concretions, glue the fossil pieces back together, then cut down to the fossil (using a diamond tip on dremel for example), then when you get close use an air scribe? I saw the CP9160 is $124 on Amazon, would that work? I saw a lot of air scribes are very expensive and out of my budget range.

Sorry for being a bit vague. Usually a hammer and maybe chisel are used to "pop", although you might be able to do it with a clamp, especially a little conc like that. The clamp is used to glue the two halves back together to help ensure a very tight fit. I avoid any rotary tools, except for maybe smoothing the rock at the end. I use my scribe to get down to and completely uncover the crab. But then again, there are many folks here that know crab prep and prep in general far better than myself. Good luck, you are staring down a very expensive rabbit hole.

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Ptychodus04
7 hours ago, Kane said:

Are you sure? Judging by the carpet fibre size in the background, the specimen seems a bit small. I know I would be leery of bringing in big ME on a small piece (I've done it, but only when I'm feeling like Super Dave Osborne :P ). If it was big (RJB standard big), I'd say ME for sure! Or, if it is going to be a glue-on job to bring the halves together and prep from the top, again, definitely 9100.

I’m thinking along the lines of gluing and prepping down from the top. If you’re going to bother, might as well do it right. :D

 

It is rather exciting to go after something delicate with a big tool. Sometimes, that’s the only option.

 

 

6 hours ago, TriloCrabs said:

Those are a bit out of my price range. After spending a few hours looking, I think I am going to call tomorrow and see what the price is of the All Air products 8315B and extended tip currently is. It seems a lot cheaper and able to do the job - there are posts on here saying it can handle crab matrix.

The 8315b should be similar to the CP8160. Both are an Aro size (middle of the road) scribe.

 

I’m not saying that they won’t handle the prep. It will take you a very long time to scribe through that much matrix. My first scribe was an Aro and I quickly learned its limitations. More massive matrices take more tool to get through in a reasonable amount of time.

 

Fossil prep is a never ending money pit. Along with the scribe comes the purchase of a plethora of other needed items: air compressor (bigger than you think you need), magnification (don’t prep without it), eye protection, hearing protection, lung protection (silicosis and pulmonary fibrosis are tough ways to die), lighting, and dust collection/remediation. Before you know it you’ve dropped around $10k and have a fully stocked prep lab in your backyard. That being said, it is one of the most rewarding things that I have gotten myself involved in.

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7 hours ago, Kane said:

Super Dave Osborne

Been a lot of years since ive heard that name.  Used to watch him on TV.

 

7 minutes ago, Ptychodus04 said:

My first scribe was an Aro and I quickly learned its limitations.

Same here Kris.   I did do a lot of crab concs with the 8315b though.  Used to prep up to around 16 hours a day too.  The ME9100 saved me a ton of time after that. 

 

RB

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TriloCrabs
7 hours ago, Ptychodus04 said:

I’m not saying that they won’t handle the prep. It will take you a very long time to scribe through that much matrix. My first scribe was an Aro and I quickly learned its limitations. More massive matrices take more tool to get through in a reasonable amount of time.

 

Fossil prep is a never ending money pit. Along with the scribe comes the purchase of a plethora of other needed items: air compressor (bigger than you think you need), magnification (don’t prep without it), eye protection, hearing protection, lung protection (silicosis and pulmonary fibrosis are tough ways to die), lighting, and dust collection/remediation. Before you know it you’ve dropped around $10k and have a fully stocked prep lab in your backyard. That being said, it is one of the most rewarding things that I have gotten myself involved in.

 

I already have a compressor, head strap magnifier, eye, hear, half face 3M P95 Respirator, lighting, dremel (lots of carbon/diamond bits), dremel engraver, chisels, hammers, files, 2 shop vacs since I do a lot of DIY and projects around the house, much purchased for cheap at estate sales. So far all I have had to buy is a $25 HF air eraser, $8 sterilite bucket to make a diy blast cabinet. It really seems the main other item is just an air scribe, and for my use-case, a reputable non-name brand seems like it will do.

 

I also am into aquariums, so I'm well aware of ballooning costs, but I also realize that there are much cheaper ways to set up an aquarium that works just as well at a fraction of the cost (e.g. you can get a 20g tank, light, filter on OfferUp ($50), potting soil ($3), low tech plant trimmings from local people (cheap/free), driftwood (free), river rocks (free), a sheet of carbon filter sponge for filter media ($6) for around $60, vs buying a 20g tank ($40), light hood ($40), filter ($30), media ($30 x 3), plants (10 x $10), wood ($50), individual filters ($20/6 mo), CO2 setup for high tech plants ($200+) for $600+). And then there are people that recommend name-brand end stuff (e.g. $200 tanks) that can easily double/triple the price tag. I'm just looking for the good enough, cheaper route. :)

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21 minutes ago, TriloCrabs said:

head strap magnifier

I might add, from my experience a head strapped magnifier is probably not ideal. For real detail work when prepping you'll want 10X magnification, maybe more depending on what you're working with. A microscope is a must have for serious prepping.

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TriloCrabs
5 minutes ago, Huntonia said:

I might add, from my experience a head strapped magnifier is probably not ideal. For real detail work when prepping you'll want 10X magnification, maybe more depending on what you're working with. A microscope is a must have for serious prepping.

It goes to 4.8X, but I do have also have a jewelers loupe and microscope.

 

Edit: Also I have a macro lens set for my camera that has wifi video out to ipad that would prob work better (pics above). I can also zoom in much more than that.

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crabfossilsteve

if you going to go down this rabbit hole, I'd recommend gluing the tow halves together with super glue and clamp them down hard.  Since you have a dremel, use a grinding "wheel" and start grinding a circular divit above where the carapace should be and keep grinding down until you just hit the carapace shell.  From there you can start using your air scribes to pulverize the matrix off the shell material.  Good luck, it a tedious job.  You might want to start on a not so good specimen.

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TriloCrabs
5 minutes ago, crabfossilsteve said:

if you going to go down this rabbit hole, I'd recommend gluing the tow halves together with super glue and clamp them down hard.  Since you have a dremel, use a grinding "wheel" and start grinding a circular divit above where the carapace should be and keep grinding down until you just hit the carapace shell.  From there you can start using your air scribes to pulverize the matrix off the shell material.  Good luck, it a tedious job.  You might want to start on a not so good specimen.

 

Thanks so much for the advice, I'm happy to see it is right along with what I had planned! Luckily I have multiple concretions from my last trip (I decided I had to go back), including one that was a partial (found part of a split concretion), and it broke as I thought putting it into a clamp meant using the clamp to pop it... All a part of the learning experience, and something I wont do again!:duh2: 

 

I've been reading dozens of forum posts on crab prep, and the best resource I found for popping concretions were your posts recommending popping with a hammer and chisel for round ones, and a defunct sites from years ago by Craboholic who lives in WA, but doesn't seem to be active any more. Luckily I found the site on archive.org: https://web.archive.org/web/20150801000000*/http://www.fossilcrabs.com/information.htm

 

Any other advice you have I would be very interested in, as I've seen some of your work as I've been reading through thread, and it's amazing! You should consider adding some images to your profile gallery. :) 

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You can get an Opti-Visor that is 10x.  

 

RB

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4 hours ago, RJB said:

You can get an Opti-Visor that is 10x.  

 

RB

I have found that the 10x is too much; you have to work about 2 inches from your face.  But this is a small crab so will need some sort of magnification.  And tons of patience.  As someone else mentioned, practice on a lesser quality crab if you can. 

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