Dealing with existing prep work on a Hell Creek dinosaur bone

[TriVeratops]

38 minutes ago, Alex S. said:

Thank you for sharing the poster that is very interesting. Keep up the good work I look forward to seeing your next update.

 

Thanks, I appreciate the encouragement!!

 

Have ordered oxalic acid. In the meantime, I’ll continue removing paint.

[TriVeratops]

I’ve been finding that denatured alcohol works just fine for the paint removal, so i’ve been using that instead of acetone. But there’s an adhesive here and there that resists denatured alcohol, I’m guessing it’s superglue. For this I’m using cotton balls soaked in acetone. I leave them on for like 30 seconds, scrape, repeat. It’s not getting rid of all of the adhesive, but just enough that the unnatural gloss disappears and the color of the bone shows through.

 

before

 

after

 

The changes are subtle, but it’s starting to look less smeary. 

 

 

Btw the butvar arrived the other day. It dissolved beautifully in denatured alcohol (I mixed it at a 5% ratio of butvar to alcohol) and I used it to consolidate the little chunk of distal blade. It drank the stuff right up and feels more substantial now.

 

Edited June 11 by TriVeratops

[TriVeratops]

Summer things got in the way for a minute, but today I had some down time and got back into it! I finished removing paint from the distal end and started on the big piece. 

 

I’m finding that in addition to being painted over, several areas of natural fossil were covered up with thin layers of plaster to smooth out the restored areas. It’s so satisfying to pop that stuff off.

 

Few more before/after pics.

 

 

 

I’m really looking forward to digging out all that plaster. One step at a time.

 

 

Edited July 4 by TriVeratops

[hadrosauridae]

You are improving this fossil immensely! Keep up the good work.  Its going to look professionally restored when you are done!

[TriVeratops]

I’ve removed enough paint to be satisfied with it, so now I’ve moved on to the plaster. 

 

A weak solution of oxalic acid and baking soda in water was enough for me to carve out all the plaster in this little section in an hour and a half or so. The solution doesn’t seem to react with the fossil at all. I could try a stronger solution to speed it up, but I’ll probably just stick with this to play it safe.

 

Before

 

Paint removed

 

Plaster looking kinda like queso fresco, yummy

 

All clean!

 

 

Edited July 11 by TriVeratops

[Sjfriend]

Excellent work! Should look great when done!

[trilobites_are_awesome]

On 7/10/2024 at 11:33 PM, TriVeratops said:

I’ve removed enough paint to be satisfied with it, so now I’ve moved on to the plaster. 

 

A weak solution of oxalic acid and baking soda in water was enough for me to carve out all the plaster in this little section in an hour and a half or so. The solution doesn’t seem to react with the fossil at all. I could try a stronger solution to speed it up, but I’ll probably just stick with this to play it safe.

 

Before

 

Paint removed

 

Plaster looking kinda like queso fresco, yummy

 

All clean!

 

 

Looking good!

[TriVeratops]

Had some free time over the weekend and made good progress.

 

my very professional workspace lol

 

looking toward the proximal end, where the most work awaits

 

 

So far I’m finding that most of the pieces are pretty well secured with superglue, but some of them don’t seem to have a lot of contact points where two pieces connect, risking future failure. Glad I’m doing this.

Edited July 15 by TriVeratops

[trilobites_are_awesome]

You are doing a great job!

[Jaybot]

Looking great!

[TriVeratops]

Nice surprise! These relatively big pieces of external bone were almost completely obscured by plaster. Pretty thrilled to find out this fossil is more complete than expected.

 

 

Edited July 16 by TriVeratops

[TriVeratops]

It’s slow going now. Much more plaster to remove at the proximal end.

 

 

 

As I get closer to the next step of replacing the plaster with a different gap fill, it’s not lost on me that I’m planning to replace a relatively reversible filler (plaster) with a relatively irreversible one (epoxy putty). 

 

So I’ve been thinking about making the epoxy fill reversible by adding a barrier layer of paraloid B72 to any surfaces that will be in contact with epoxy putty. Paraloid isn’t as strong an adhesive as cyanoacrylate or epoxy, but according to this paper (Russell & Strilinsky, 2016: “Keep It Together: An Evaluation of the Tensile Strengths of Three Select Adhesives Used in Fossil Preparation,” Collection Forum), it still makes a very strong bond. Also, for this project, the paraloid (and the epoxy adhering to the paraloid) would only function as secondary adhesives because the fossil will be mostly held together with superglue from the original prep job.

 

So, theoretically, if somebody wanted to undo this resto someday, they could give the joins an acetone soak and take them apart. Acetone would not completely dissolve the superglue that’s already there, but it would at least soften enough that somebody could remove most of it if they really wanted to.

 

Thoughts on this course of action? 

Edited July 28 by TriVeratops

[TriVeratops]

I found another study (Podany, Garland, Freeman & Rogers, PARALOID B-72 AS A STRUCTURAL ADHESIVE AND AS A BARRIER WITHIN STRUCTURAL ADHESIVE BONDS: EVALUATIONS OF STRENGTH AND REVERSIBILITY, JAIC 2001, Volume 40, Number 1, Article 2, pp. 15 to 33), that supports the specific use of B72 as a reversible barrier layer for an irreversible adhesive in applications that require great bond strength (in this case, large ancient marble sculptures). From the conclusions:

 

“The test results suggest that the application of a barrier, if relatively thin, conformal, fully continuous, and fully dried (solvent free) before the introduction of a secondary adhesive, provides a considerable degree of reversibility to a joint without decreasing the needed strength required to sustain either shear or tensile loads imposed on most structural bonds made for the reassembly of large stone sculpture. It appears that the B-72 is sufficiently strong to safely be part of a structural joint and to provide a reversible barrier between the substrates and the less reversible structural adhesive. However, the B-72 barrier must be fully dry. This state can be achieved by applying a thin barrier on both faces of the joint when both substrates are fully exposed and can easily lose solvent prior to the application of the structural adhesive.”

[trilobites_are_awesome]

What paraloid/glue are you using?

[TriVeratops]

1 hour ago, trilobites_are_awesome said:

What paraloid/glue are you using?

 

Based on the studies above, I’m ordering Paraloid B-72 as the barrier layer for the gap fill. I have Butvar B-76 on hand, but the latter is not indicated for use as a structural adhesive with large fossils.

[TriVeratops]

Flipped it over this weekend to work on the other side.

 

Before

 

Paint removed

 

Scored with dental pick to allow entry of oxalic acid solution

 

Half of plaster removed

 

Rest of plaster removed. Part of this will be covered up again with putty, but I’ll probably keep most of the bone in the upper middle uncovered because it appears to be exterior bone that was crushed inward.

Edited July 29 by TriVeratops

[Jaybot]

It's looking great!  You must have a large amount of patience

[TriVeratops]

1 hour ago, Jaybot said:

It's looking great!  You must have a large amount of patience

 

Thanks! This project is requiring a lot of patience for sure. It’s not too bad though…brew some tea, put on Spotify, scrape away plaster little by little. It’s relaxing.

[TriVeratops]

Got distracted by a little thing, but I’m back on the plaster, doin it faster, still haven’t had a single disaster 

 

 

Been listening to a podcast called Terrible Lizards while I work. 10/10, would recommend.

 

[hadrosauridae]

Looking great!  Just use caution because you are also removing support.  I've been thinking about some of your recent posts.  I think your plan to isolate each piece with paraloid before adding in epoxy putty is a futile effort.  While I applaud the effort to keep you work "reversible" its not really needed.  Its not going into a museum collection, its not going to be studied for research, thus, there is no need to keep all the elements pure.  

 

The work you have done to remove the poor quality prep is wonderful.  If this were mine, I would simply make sure the bone sections were well consolidated, and then fill the voids with epoxy which also is a great bonder to strengthen the specimen as a whole.

[TriVeratops]

Yeah, I’m definitely getting into a dangerous area re: removal of the support. So far it’s holding up well, but I think I’ll do some consolidating before I continue. 

 

I appreciate the viewpoint about reversibility. However, I don’t think what I’m envisioning is all that different from what you’re advising. It’s just adding a layer of consolidant/adhesive, which I’ll already be using to strengthen the bone, on the interior surfaces that will be in contact with the epoxy. This doesn’t really require any extra effort and should still be plenty strong enough to hold the fossil together. Maybe I’ll eat my words if it falls apart in my hands, but the studies above suggest otherwise…and if it does fall apart, at least I can redo it 

 

It’s not so much about being scientific or facilitating research as it is about recognizing that fossils change hands, and aesthetic preferences and preparation modes also change. I see a lot of fossils that have resto work I wouldn’t have advised and would want to undo/redo if they came into my possession.  And for that matter, some future collector may not like my work and might want to change it. (That future person may be me, I like do-overs)

[hadrosauridae]

3 hours ago, TriVeratops said:

Yeah, I’m definitely getting into a dangerous area re: removal of the support. So far it’s holding up well, but I think I’ll do some consolidating before I continue. 

You might consider doing some epoxy filling as you go, so you dont end up with just the unknown glue joints remaining.  That will help alleviate some support concerns.

 

3 hours ago, TriVeratops said:

 

I appreciate the viewpoint about reversibility. However, I don’t think what I’m envisioning is all that different from what you’re advising. It’s just adding a layer of consolidant/adhesive, which I’ll already be using to strengthen the bone, on the interior surfaces that will be in contact with the epoxy. This doesn’t really require any extra effort and should still be plenty strong enough to hold the fossil together. Maybe I’ll eat my words if it falls apart in my hands, but the studies above suggest otherwise…and if it does fall apart, at least I can redo it  

Ok, that is what is called consolidating the bone and is almost always a good idea.

 

 

3 hours ago, TriVeratops said:

 

It’s not so much about being scientific or facilitating research as it is about recognizing that fossils change hands, and aesthetic preferences and preparation modes also change. I see a lot of fossils that have resto work I wouldn’t have advised and would want to undo/redo if they came into my possession.  And for that matter, some future collector may not like my work and might want to change it. (That future person may be me, I like do-overs)

OK, I see your goal, and I think that is very commendable of you.  

[TriVeratops]

1 hour ago, hadrosauridae said:

You might consider doing some epoxy filling as you go, so you dont end up with just the unknown glue joints remaining.  That will help alleviate some support concerns.

 

good call, will definitely reinforce the joints as I go! 

[TriVeratops]

I noticed early on that the pseudoacromion process (i think that’s what it’s called) was glued incorrectly and needed to be rotated  several degrees clockwise to get it to fit. Since I’m starting to reinforce the joins, it’s finally time to redo this one. 

 

Before

 

After

 

To the right of the pseudoacromion process, there was a clump of leftover matrix that the prepper painted over. I managed to remove most of it today. More exterior bone underneath!

 

The middle area here was completely covered with matrix.

 

Little by little, it’s coming along!

[hadrosauridae]

Nice. The repairs you show, the more I wish the original prepped would stop touching fossils completely. 

 

Looking at the cleaned surface, it looks to have a pretty significant separation and matrix infill along this line. Curious if you are planning on correcting those lines, and your plan.