Butvar B-76 Mixing Ratios

[Allosaurus]

I was hoping somewhere here could tell me what is commonly used as a mixing ratio for butvar B-76 and acetone. I'm needing to harden some of my fossils, and put a few back together.

[Mattalic]

This will be of use to you: http://www.thefossilforum.com/index.php?/topic/48399-a-rookies-attempt-at-a-consolidated-guide-to-fossil-consolidation-butvar-76/

[Allosaurus]

Thank you. I read through all the articles, but I'm still having problems. When I apply the B-76 and allow it to dry, one of my fossils (a ceratopsian rib) wants to crumble up. Any suggestions on how to prevent this?

[rejd]

Can you post a pic of the rib? is it really crumbly to begin with? You may need to consolidate it with a very thin mixture ( I use a 5% weight/volume mixture) to consolidate.

[Harry Pristis]

Can you post a pic of the rib? is it really crumbly to begin with? You may need to consolidate it with a very thin mixture ( I use a 5% weight/volume mixture) to consolidate.

Can you please translate "a 5% weight/volume mixture" into other words? How much Butvar-76 do you dissolve in how much acetone to arrive at such a concentration?

[rejd]

I mix 5g into 100ml of acetone to achieve this. Here is an exert from a paper on adhesives:

Weight-to-Weight versus Weight-to-Volume

Adhesive and consolidant solutions can be prepared either by combining specific weights of polymer and solvent (w/w) or by combining a specific weight of polymer and a specific volume of solvent (w/v). In each case, the resulting concentration can be expressed as a percentage. For most uses on fossil vertebrates the difference is not critical.The important point is to properly indicate on the container label and in your documentation which method you are using to prepare your solutions and to designate the units of measure used (w/w or w/v).

Edited November 16, 2014 by rejd

[Harry Pristis]

Thank you.

[rejd]

your welcome. Here is a link to the paper if anyone is interested.

http://www.academia.edu/1237393/Paraloid_B-72_Practical_Tips_for_the_Vertebrate_Fossil_Preparator

[Allosaurus]

This was the piece I experimented with. It was a little crumbly before but afterward it turned super crumbly. I've tried 3 tablespoons per 800 ml and 1/8th of a teaspoon mixed with 120 ml.

I also treated a piece of the matrix that was not crumbly, and it seemed like the acetone was breaking the matrix down to make it crumbly.

Edited November 17, 2014 by Allosaurus

[Opisthotriton]

Yes, acetone will weaken that type of bone, so make sure the bone is well supported (on something like wax paper rather than held in your hand), drip on the mixture slowly, letting it soak in drop by drop, and most importantly, DO NOT touch the bone again until it is completely dry.

[Allosaurus]

That is what I tried the 1st time. I waited for 2 to 3 hours for drying, should I wait longer? I didn't smell any acetone afterwards.

How much should I drip on?

Edited November 17, 2014 by Allosaurus

[Harry Pristis]

I've never encountered bone that became more crumbly with the application of acetone. I suspect that it's not the acetone per se that is the problem. I think that the application of any fluid might liberate pieces of freeze/thaw-shattered bone.

The co-efficient of friction is high in the joints of fractured-but-not-disaggregated bone. The addition of any fluid will lubricate the joints in fractured bone for the brief time before the fluid boils off. Opisthotriton's advice to not handle the bone too soon after the consolidant bath is correct.

But, the Butvar-76 consolidant should have produced an infrastructure that would hold the bone together. Sooo . . . I suspect that the bone was not submerged/bathed in the consolidant long enough or thoroughly enough to allow the plastic to penetrate the bone. Orrr . . . The solution was too weak to bind the microfractures together. Or both.

You did dribble the plastic beads into the acetone, rather than vice versa, didn't you? If you pour acetone onto the beads, you'll have a devil of a time getting the plastic to dissolve. That is one possible explanation for a weak solution -- the plastic may still be at the bottom of your mixing jar.

Edited November 17, 2014 by Harry Pristis

[Allosaurus]

The B76 was placed in the acetone but I do have the powder version of B76.

I submerged the bone until there was no more fizzing so that was about 30 to 45 seconds. Should I go longer and how long should I let it dry?

[Harry Pristis]

"No more fizzing" is comparable to my own timing standard. So, your solution is likely to be too weak.

I am unaware of a form of Butvar-76 other than the granulated form . . . beads about the size of table salt crystals.

Time for boiling off the acetone is variable, depending on temperature and air circulation. On those rare occasions when I am rushed, I may put the damp bone back under an infrared lamp for two or three minutes (of course, here in Florida I don't deal with freeze/thaw shattered bone).

[jpc]

Do not submerge it in Butvar. As ophis suggested, use an eyedropper and drop the hardener on one drop at a time. Do one side completely and let it dry, then roll it over and do another side, and another side. You don't need to let every drop dry, but you should let one side completely dry before you move it. Any bone like this that is wet with butvar or vinac is just waiting to fall apart if you move it while it is wet. Let it dry overnight if you must.

Edited November 17, 2014 by jpc

[ZiggieCie]

Here is a link to an excellent article on Paraloid 72. It may have some useful ideas and techniques for consolidants.

http://www.connectingtocollections.org/wp-content/uploads/2014/02/Davidson_and_Brown_2012_Paraloid_B-72-_Practical_tips_for_the_vertebrate_fossil_preparator.pdf

[tooth_claw]

Do not submerge it in Butvar. As ophis suggested, use an eyedropper and drop the hardener on one drop at a time. Do one side completely and let it dry, then roll it over and do another side, and another side. You don't need to let every drop dry, but you should let one side completely dry before you move it. Any bone like this that is wet with butvar or vinac is just waiting to fall apart if you move it while it is wet. Let it dry overnight if you must.

I second this method! I have worked with bone that crumbles like this and the way to deal with it is to support the bone (I use a bed of sand) and slowly drip in thin mixtures of consolidant. Be patient and treat a little bit of the specimen at a time so that it does not go soggy and crumble to bits. Take a week to consolidate if you need to. When it is solid, you can clean the surface of any sand that has adhered with a bit of acetone and a brush.

Good luck!

[Harry Pristis]

I defer to those with experience with crumbly bones. An eye dropper may be the best applicator for your bones.

A length of Saran Wrap draped over the supporting sand box will prevent sand from adhering to the newly-consolidated bone.

[rejd]

Good call on the saran wrap under the bone. It certainly helps keep the sand from sticking. As for applying the butvar/paraloind, i use a syringe with a 27 gauge needle. Mixed at 5% W/V it flows really nicely through the needle. Also, if you push a bit harder on the syringe the glue with squirt out in a nice stream and I use this to spray onto very weak bone. The nice thing with the 27 gauge needle as well is it is super thin and can get into very small cracks to get the glue deeper into the bone.

[Allosaurus]

Will defintely use the Seran wrap. Great idea with the syringe!

I was talking to a fossil preparater at MOR and she suggested mixing at 2 cups of b76, to a gallon of acetone. Also she said something very interesting. It sounds like it actually is the B-76 that can cause a fossil to crumble if it is very delicate, not the acetone.

I've got the new mixture mixed together so I'm just waiting for it to completely dissolve and then I'll try it on the fossil again. Will post pictures if it turns out that it works.

Edited November 18, 2014 by Allosaurus

[Harry Pristis]

Will defintely use the Seran wrap. Great idea with the syringe!

I was talking to a fossil preparater at MOR and she suggested mixing at 2 cups of b76, to a gallon of acetone. Also she said something very interesting. It sounds like it actually is the B-76 that can cause a fossil to crumble if it is very delicate, not the acetone.

I've got the new mixture mixed together so I'm just waiting for it to completely dissolve and then I'll try it on the fossil again. Will post pictures if it turns out that it works.

Hmmm. Sixteen fluid ounces of B-76 beads dissolved in 128 fluid ounces of acetone would give you 12.5% solution by volume. That is, I think, much more concentrated than I have ever found useful. But, maybe that is what is necessary for crumbly dino bones.

A preparator is sometimes more artist than scientist. Blaming the B-76 (versus the liquid medium) for the breakdown of bone sounds more like imagination than science. What was her explanation for this assertion?

[Opisthotriton]

MOR uses Vinac B-15 beads, so the "cup volume" might contain more air than a cupful of butvar beads/powder?

As for blaming the plastic rather than the acetone, I interpret that as most likely an error in communication/interpretation. The preparator may have used the term vinac/butvar loosely and really meant the acetone component of the solution.

The concentration of butvar/vinac to acetone can vary a lot for different purposes, depending on the bone. A thicker solution might just sit on the surface of the fossil without penetrating very far, while a thinner solution may penetrate well but not carry enough plastic into the bone to make it worthwhile (acetone weakening the bone and not leaving enough plastic behind when it evaporates). You might want to make several small jars and try adding a little more acetone or butvar to each to find the perfect ratio for your needs. I accidentally forgot the mixing ratio once, and only used one cup of beads per gallon, and the result was so weak that after application it was hard to tell any plastic had been applied at all. But at least it's a forgiving solution, and you can always mix in more acetone or butvar later.

Also, butvar/vinac can take a long time to dry, especially when thick or in a humid climate. A light coat of thin butvar in a dry climate can be pretty dry in half an hour, but a soaking of thick butvar can take 6 hours to be somewhat stable, and would need at least 24 to be fully dry and hard. In a very humid climate, it would take even longer.

[tooth_claw]

_{"A preparator is sometimes more artist than scientist." Very true Harry Pristis. I have worked with these solutions for many years and have never used a standardized recipe or mix ratio- I just mix up whatever thickness I require, from a thick glue to a watery penetrating fluid depending on the individual fossil. As Opisthotriton mentioned, you can always experiment with the mix as you go.}

[Harry Pristis]

MOR uses Vinac B-15 beads, so the "cup volume" might contain more air than a cupful of butvar beads/powder?

As for blaming the plastic rather than the acetone, I interpret that as most likely an error in communication/interpretation. The preparator may have used the term vinac/butvar loosely and really meant the acetone component of the solution.

The concentration of butvar/vinac to acetone can vary a lot for different purposes, depending on the bone. A thicker solution might just sit on the surface of the fossil without penetrating very far, while a thinner solution may penetrate well but not carry enough plastic into the bone to make it worthwhile (acetone weakening the bone and not leaving enough plastic behind when it evaporates). You might want to make several small jars and try adding a little more acetone or butvar to each to find the perfect ratio for your needs. I accidentally forgot the mixing ratio once, and only used one cup of beads per gallon, and the result was so weak that after application it was hard to tell any plastic had been applied at all. But at least it's a forgiving solution, and you can always mix in more acetone or butvar later.

Also, butvar/vinac can take a long time to dry, especially when thick or in a humid climate. A light coat of thin butvar in a dry climate can be pretty dry in half an hour, but a soaking of thick butvar can take 6 hours to be somewhat stable, and would need at least 24 to be fully dry and hard. In a very humid climate, it would take even longer.

I hadn't given much thought to dinosaur bones or to any other bones that have sustained freeze/thaw fractures. Based on this thread and other comments, I can see how acetone, like any other fluid, could cause such a bone to come apart. That has never been a challenge with bones in Florida. With Florida fossils, the ideal consolidation is: after application it was hard to tell any plastic had been applied at all. I suppose I should add a disclaimer to the suggested technique in my forum profile.

[Harry Pristis]

_{"A preparator is sometimes more artist than scientist." Very true Harry Pristis. I have worked with these solutions for many years and have never used a standardized recipe or mix ratio- I just mix up whatever thickness I require, from a thick glue to a watery penetrating fluid depending on the individual fossil. As Opisthotriton mentioned, you can always experiment with the mix as you go.}

You clearly are an experienced preparator. I, too, use the consistency of consolidant that seems correct for the fossil, never using a standard recipe. That intuition-based operation is pretty easy with Florida fossils which are usually undemanding when it's time to consolidate.

I resisted for a long time the requests for a ratio of plastic to acetone, favoring the intuitive "small air bubble are slightly retarded in their rise to the surface." That has worked for me for more than 30 years here in Florida. It seems when you try to pin down the "correct" ratio, new considerations arise.