Looking for advice on how to repair a long bone with a missing center piece

[uncoat]

I just returned from a collecting trip and to my dismay i realized that i am missing a piece of a fossil bone i collected.. The bones at this site are in concretions and are not always visible on the outside so a lot of the time they have to be broken to know for sure what is inside. I thought i had a fairly clean break but when i got home and re assembled the pieces, it seems that one section of the bone is missing in the center. I have delt with small problems similar to this before by filling the missing space with Durham's putty and sculpting it on the edges. With this fossil, an entire section of bone is missing. So i will want to reassemble the rock and fill the section before i start in of prepping it so i know exactly how wide the space is. My concern is that  something like Durham's wont be strong enough to support the full strength of the bone during and after preparation. Can anyone suggest a similar sculpt-able putty that would not shrink and dry incredibly hard?

 

Since the concretion is in pieces its hard to photograph in a way that conveys what i mean so i drew a picture of the problem.

 

Nick

 

 

[caldigger]

Nick, do you have access to a heat gun?

Not a hair dryer, you need higher heat.

I have had incredible success with a product called Sculpey lll. It is a "oven bake" modeling clay that does not shrink has high strength when dry and is very easy to use. Available at crafts stores ( I get it at Micheals ).

I use a heat gun, the kind to assist in paint removal. 

 

Here are some examples of my repairs.

 

The whole center section of this Mammoth tooth arrived in the mail in crumbs. I filled it in with Sculpey lll.

The left side of the root was missing when I dug up this tooth. Reconstructed with Sculpey.

 

Just knead the clay until it is the softness you want to work with, shape it and work the heat gun on it for a few minutes, let it cool down and you are ready for painting.

The clay comes in many colors and you could probably get some different colors to mix together for the closest color match for your bone.

Each package only cost about $1.20 so it is an inexpensive fix.

[Ptychodus04]

@uncoat, I like Apoxie Sculpt. It is a 2 part epoxy clay. Once mixed, it can be worked just like any sculpting clay for about 2 hours. It is self curing, sand-able, and paint-able once cured (6 hours I believe).

 

I would stabilize the bone ends with Paraloid and then glue the two pieces of concretion back together prior to restoring the missing bone section. Then, scribe the concretion away from the bone, starting near the broken ends. If done carefully, under magnification, the matrix can be removed without breaking off the ends of the bone. This will allow you to better shape the sculpting medium of your choice to the actual shape of the bone prior to curing. If you apply the sculpting medium prior to removing the matrix, you will have a lot more sanding and grinding to do in order to properly shape it to match the bone.

[uncoat]

@caldigger, Man i forgot about Sculpey. I used to make things out of it as a kid. Your restorations look great! I cant tell where or what you restored. I will have to look into getting a heat gun and some sculpey III next time im near a craft store. Thanks for the good info.

 

@Ptychodus04, Thanks for the info! That's exactly the sort of tip i was looking for. I will get it back together and scribe it out around the break and then figure out what i want to use for the fill before prepping the rest out. I will have to look up apoxie Sculpt as im unfamiliar with it.

 

Nick

[siteseer]

Caldigger,

 

Wow, you do good work.  That tooth looks nice.

 

Jess

[siteseer]

On 3/26/2019 at 5:41 AM, Ptychodus04 said:

@uncoat, I like Apoxie Sculpt. It is a 2 part epoxy clay. Once mixed, it can be worked just like any sculpting clay for about 2 hours. It is self curing, sand-able, and paint-able once cured (6 hours I believe).

 

I would stabilize the bone ends with Paraloid and then glue the two pieces of concretion back together prior to restoring the missing bone section. Then, scribe the concretion away from the bone, starting near the broken ends. If done carefully, under magnification, the matrix can be removed without breaking off the ends of the bone. This will allow you to better shape the sculpting medium of your choice to the actual shape of the bone prior to curing. If you apply the sculpting medium prior to removing the matrix, you will have a lot more sanding and grinding to do in order to properly shape it to match the bone.

 

Yes, I would use 2-part epoxy putty too.