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Help patching missing bone fragments


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NevadaHunter

Hi all,

 

I know this topic has been hammered pretty hard but I just don’t feel I’ve seen the answers I’m looking for. I have a few long bones I’m gluing back together with some Paraloid B-72, and I was hoping to get advice on reversible materials I can use to patch the missing holes. I’d like the color to generally match but still have it be obvious it’s a repair. Also, what do you all store your paraloid solutions in, I’ve tried mason jars but those seals dissolve so quickly! I need something to get in and out of quickly as some of these long bones have taken over 20hrs of prep and I am constantly gluing. I’ll be hopefully finishing up a camel radioulna soon that I’ll be posting! 

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17DE8B1D-AE03-44BA-AD3B-A71906A7FF67.jpeg

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I don't know about a reversible filler?  You could maybe use epoxy putty that you buy in different colors or color yourself with masonry powders.  I have had to remove some of this epoxy putty in the past but had to carefully remove it mechanically.  Good luck

 

RB

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hadrosauridae

Paraloid certainly wouldnt be my go-to for repairs like youre doing.  Its better as a removeable glue than as a permanent joint.  For the filler, an epoxy putty is probably you best choice because it wont shrink or swell.  With the amount of white on this fossil, I would just use a plain white or off-white putty.  It will blend well enough. Of course, thats if the white we can see is a permanent color and not just a surface coating that will be prepped off later.  

 

For the consolidate storage, I had to do a lot of research for the answer!  Look for a plastic mason jar lid by a company called "iLIDS".  The type of plastic used isnt degraded by the acetone.  I've had mine in use for a year and they are still sealed and solid

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Ptychodus04

I use a mason jar with saran wrap between the jar and the lid. This doesn't degrade from the acetone. And it helps to keep the glue off the threads.

 

I regularly use Paraloid for permanent glue joints that don't bear a lot of weight. It is preferable to other glues that can degrade over time.  What is the logic behind reversing the restoration? Typically, if you think you might reverse the assembly for some research purpose, you would not restore the specimen. Restoration is, for the most part, for display purposes. If you plaan to take the piece apart, don't restore it. If you plan to leave it together indefinitely, use a slow set epoxy putty like Apoxie Sculpt.

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27 minutes ago, Ptychodus04 said:

I use a mason jar with saran wrap between the jar and the lid. This doesn't degrade from the acetone.

 

Thanks for that tip! 

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NevadaHunter
5 hours ago, hadrosauridae said:

Paraloid certainly wouldnt be my go-to for repairs like youre doing.  Its better as a removeable glue than as a permanent joint.  For the filler, an epoxy putty is probably you best choice because it wont shrink or swell.  With the amount of white on this fossil, I would just use a plain white or off-white putty.  It will blend well enough. Of course, thats if the white we can see is a permanent color and not just a surface coating that will be prepped off later.  

 

For the consolidate storage, I had to do a lot of research for the answer!  Look for a plastic mason jar lid by a company called "iLIDS".  The type of plastic used isnt degraded by the acetone.  I've had mine in use for a year and they are still sealed and solid

Thank you for the advice! What sort of products would you recommend in place of paraloid? 

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Ptychodus04
2 hours ago, NevadaHunter said:

Thank you for the advice! What sort of products would you recommend in place of paraloid? 

Museums use Paraloid or Butvar for all glue joints that aren’t on heavy bones (for the most part). For bones like the example you showed, it works very well. Many collectors use cyanoacrylate glues but they are comparatively weak. The provide a strong bond but are brittle. I only use it when I have flat pieces that are getting glued and clamped together, like a fish that is sheared in half and bits are on both sides of the break.

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hadrosauridae
2 hours ago, NevadaHunter said:

Thank you for the advice! What sort of products would you recommend in place of paraloid? 

 

1 minute ago, Ptychodus04 said:

Museums use Paraloid or Butvar for all glue joints that aren’t on heavy bones (for the most part). For bones like the example you showed, it works very well. Many collectors use cyanoacrylate glues but they are comparatively weak. The provide a strong bond but are brittle. I only use it when I have flat pieces that are getting glued and clamped together, like a fish that is sheared in half and bits are on both sides of the break.

 

Well, apparently I'm wrong and paraloid is a good option.  You know what they, try to learn something new every day.  Just try to avoid the lesson with your foot in your mouth, LOL

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Ptychodus04
14 hours ago, hadrosauridae said:

Well, apparently I'm wrong and paraloid is a good option.  You know what they, try to learn something new every day.  Just try to avoid the lesson with your foot in your mouth, LOL


You’re less often wrong than you are right. You’ve never suggested using white glue on wet fossils. :default_faint::P
 

Cyanoacrylate has its place. I once had to assemble a bird scapula that was only 2.5” long and was broken into 27 pieces (with breaks on three different planes nonetheless). I consolidated the individual pieces and used cyanoacrylate for the assembly. Paraloid would have been a terrible choice here.

 

On the other end of the spectrum, I had a massive phytosaur skull in a sandstone block to put back together, I used clear (non-expanding) gorilla glue for this one due to the weight. Paraloid would have been a poor choice here due to the extreme weight.

 

It’s kind of a Goldilocks glue. It likes conditions that are not too big and not too small. :P

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NevadaHunter
14 hours ago, Ptychodus04 said:


You’re less often wrong than you are right. You’ve never suggested using white glue on wet fossils. :default_faint::P
 

Cyanoacrylate has its place. I once had to assemble a bird scapula that was only 2.5” long and was broken into 27 pieces (with breaks on three different planes nonetheless). I consolidated the individual pieces and used cyanoacrylate for the assembly. Paraloid would have been a terrible choice here.

 

On the other end of the spectrum, I had a massive phytosaur skull in a sandstone block to put back together, I used clear (non-expanding) gorilla glue for this one due to the weight. Paraloid would have been a poor choice here due to the extreme weight.

 

It’s kind of a Goldilocks glue. It likes conditions that are not too big and not too small. :P

At what point would you consider the job too big for paraloid? As of this current moment, my biggest bone isn't much larger than the one pictured- roughly 26 inches in length but it was removed in 6" sections constituting a few hundred pieces. The roots have badly broken these bones as the strata they're at is now near the surface. I figured since paraloid is reversible, it would be most helpful for putting together these large puzzles that may not always fit together perfectly the first time around. 

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Ptychodus04
9 hours ago, NevadaHunter said:

At what point would you consider the job too big for paraloid? As of this current moment, my biggest bone isn't much larger than the one pictured- roughly 26 inches in length but it was removed in 6" sections constituting a few hundred pieces. The roots have badly broken these bones as the strata they're at is now near the surface. I figured since paraloid is reversible, it would be most helpful for putting together these large puzzles that may not always fit together perfectly the first time around. 

I wouldn’t expect Paraloid to hold more than 10-15 pounds of force but everything is subjective. A porous bone with well fitting breaks will allow for a much stronger bond than a dense fossil with ill fitting breaks. This is because the Paraloid can soak into the porous bone, filling in the holes and making a very deep penetrating joint. This is unlikely to shear off.

 

The best thing about it is the reversibility. I have no concerns slathering it onto a bone and cleaning it up later if it runs.

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Harry Pristis
9 hours ago, Ptychodus04 said:

I wouldn’t expect Paraloid to hold more than 10-15 pounds of force but everything is subjective. A porous bone with well fitting breaks will allow for a much stronger bond than a dense fossil with ill fitting breaks. This is because the Paraloid can soak into the porous bone, filling in the holes and making a very deep penetrating joint. This is unlikely to shear off.

 

I've lost track of which Paraloid, glue or consolidant, is being referenced in this thread.  I get the sense that I am not the only one.  It seems to me that there should not be any porous bone being glued -- all the pieces to be glued should be well-consolidated beforehand.

 

I agree with Hadrosauridae that, once glued together in a satisfactory form, the gaps should be filled in with epoxy putty.  Putty because it is so manageable.  If there is any question of stability, you can leave one gap open into which you can inject 5-minute epoxy using a disposable syringe. Rotate the bone to line the interior with the epoxy.  (Uncured epoxy can be dissolved away with rubbing alcohol.)  Bamboo barbecue skewers can be pre-placed inside the bone for increased rigidity.  I haven't had to do this epoxy lining very often, but any long, thin bone is a candidate. 

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Ptychodus04
2 hours ago, Harry Pristis said:

 

I've lost track of which Paraloid, glue or consolidant, is being referenced in this thread.  I get the sense that I am not the only one.  It seems to me that there should not be any porous bone being glued -- all the pieces to be glued should be well-consolidated beforehand.

B72 is the Paraloid being used. Agree that consolidation beforehand is imperative. The point I was making was that the paraloid will penetrate deeply and make an extremely secure bond.

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Harry Pristis
2 hours ago, Ptychodus04 said:

B72 is the Paraloid being used. Agree that consolidation beforehand is imperative. The point I was making was that the paraloid will penetrate deeply and make an extremely secure bond.

 

This is a good illustration of the ambiguity that has crept into this thread.  You didn't make a distinction here between thicker Paraloid (glue) and thin Paraloid (consolidant).  They are not interchangeable -- one will make a secure bond, the other will penetrate deeply.  They may be used in conjunction with one another, but one does not substitute for the other.

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Ptychodus04
11 hours ago, Harry Pristis said:

 

This is a good illustration of the ambiguity that has crept into this thread.  You didn't make a distinction here between thicker Paraloid (glue) and thin Paraloid (consolidant).  They are not interchangeable -- one will make a secure bond, the other will penetrate deeply.  They may be used in conjunction with one another, but one does not substitute for the other.


There were some assumptions made that the OP had a general working knowledge of conservation procedures as the discussion was on the merits of Paraloid as a glue, not as a consolidation material. If that was not clear enough, mea culpa.

 

That being said, we have deviated from the OP’s original topic.
 

 

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Harry Pristis

Thanks for the explanation.  I like to remember that hundreds of collectors will read this thread eventually.  Most will be looking for information on technique, most will have no experience with Paraloid or restoring bones.  It is important to those readers to explain a technique with minimal assumptions of existing knowledge or experience.   

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NevadaHunter

Thank you all for your input, it is incredibly valuable both to myself and future users as everything I have learned came from this forum. I will look into an epoxy putty for the gaps in my specimen. Also, for the purposes of informing future users that may see this, what percent weight to volume would you recommend to use B-72 as a glue versus a consolidated?

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Ptychodus04
On 5/21/2021 at 9:33 PM, NevadaHunter said:

Thank you all for your input, it is incredibly valuable both to myself and future users as everything I have learned came from this forum. I will look into an epoxy putty for the gaps in my specimen. Also, for the purposes of informing future users that may see this, what percent weight to volume would you recommend to use B-72 as a glue versus a consolidated?

I measure my solutions with approximate ratios (solvent:plastic) by weight. For consolidation, I like a 50:1 solution. For glues, the ratio can vary significantly. I've used solutions of 20:1 for a viscosity similar to honey and as low as 5:1 for an extremely low viscosity glue. Note that the lower the viscosity, the longer it takes to make the solution and very low viscosity Paraloid isn't pleasant to work with as it likes to be sticky and stringy.

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