Butvar B-76 Question

[BisonJim]

Sorry to bother you. I've been here under "BisonLatifrons" but forgot my password and my e-mail changed. I have searched the forum (and the web) but failed to find what I'm looking for. Maybe my search skills are not good.

Anyway, while I have found a lot about Butvar 76, the specific logistics of use are missing:

What ratio do I mix it with acetone? I have a kilo (2.5 pounds or so) of Butvar B-76. I have 5 or 6 dry old holocene bison skulls falling apart. Can I put it in a plastic bucket or will the acetone or Butvar mess with that plastic? I supposed I should dip the skulls if possible, but I may have to paint it on if I can't find a large enough container of the proper material to hold it all. How do I mix it? With a cordless drill and a paint mixer? Or just stir it with a stick? How will I know when it's properly mixed? If I dip them and lay them on a table to dry, will they stick to the table? Anyway around that? I'm dealing with some whole skulls and some broken pieces that, once consolodated, I will be gluing back together. This is not museaum quality stuff. Some may even hang outside. Others on a shelf in my man cave. I just want to stop their chalky degredation. Thanks in advance.

[Wendell Ricketts]

There's no specific ratio. The more powder you add (or the less acetone), the thicker and more syrupy the solution will be. I usually add a few heaping teaspoons at a time to a liter or so of acetone and then either add more acetone to thin or more powder to thicken. You'll want to let it sit for a while because it doesn't all dissolve instantly. Ideally, the solution is perfectly clear and easy to paint. If it's too thick, you wind up getting a sort of membrane on the fossils that I personally don't like. Maybe if you're putting stuff outdoors, it'd be OK. In any case, you want to make sure that your fossils are completely dry before you put Butvar on them, or you'll get a cloudy covering.

On a project like yours, my advice would be to paint a coat or two and let dry completely to consolidate the pieces before you try dipping. The other problem with dipping, especially with big pieces, is: where are you going to put them while they dry? The Butvar will cause the fossils to stick to anything you set them on. I've had some luck rigging up temporary drying stands by twisting lengths of old wire hangers. I don't know how that would work for anything real big.

A stick or a throwaway wooden spoon is perfectly fine for mixing. You don't want anything too energetic because it'll put bubbles in the mixture that take forever to dissipate. I also wouldn't use anything electrical that might throw a spark while I was using acetone.

I don't make huge quantities at a time but, when I do make Butvar, I mix first with a spoon, gently shake the closed container, and let it stand for 24 hours. You could get away with less, but that's my method.

You can store the Butvar powder in plastic bag or glass/plastic container. In my experience, the mixed solution needs to go in glass because the acetone will eat anything plastic. No matter how air-tight you think it is, the acetone will start to evaporate and the solution will thicken until it solidifies. Best not to waste by not making more than you think you'll use in any one sitting. Only slightly thickened solution can, of course, be "revitalized" with a little more acetone.

[BisonJim]

Thanks Wendell Ricketts:

I'm off to town for the acetone and to look around at some containers and brushes. How long does it take for this stuff to dry? Thanks again for the help.

[Opisthotriton]

I second Wendell's advice. I use Vinac, a close relative of Butvar, and usually use 16oz (two yogurt cups full) per gallon. You may want it slightly thinner to ensure that it penetrates the bone. Give it about 24 hours to dissolve, and slosh it around a couple of times. You don't need to stir. Colorado shouldn't have a humidity problem; just try not to use the Butvar on rainy days. Acetone does not eat all plastics, only certain kinds. I have found that hard, clear plastics will melt in acetone. More flexible, opaque plastics (like yellow mustard bottles) make great Vinac/Butvar containers, especially if they have a good lid that lets you squirt or drip it slowly onto the bone. If you're not sure which kind of plastic you have, then make sure the container is in a tray or something so it won't make a mess in case it melts; I've seen hard plastic jars reduced to puddles of goo by acetone. Glass jars are a safe bet, they just don't have squirt-top lids.

For brushing it on, pick brushes with natural bristles; some plastic bristles (but not all) will melt in the acetone.

[Scylla]

sounds like you want to stick to polypropylene containers for the acetone

[Wendell Ricketts]

It dries really fast - acetone evaorates even faster than alcohol. That's good advice about using a thinner mixture to ensure better penetration - I should have thought of that. When you're buying brushes, it's worth spending a little more to get natural hair - I've had the bristles of a number of cheap ones disintegrate in acetone.

[jpc]

A few notes on plastics and acetone. The little recycle numbers on the bottom are the key... NUmber 2 is the best... mustard, shampoo, etc. 3 is right out as acetone will eat it vrather quickly. And I don't know about number 1. Just make sure you get all the mustard and shampoo out. The best I've used is Nalgene bottles with a plastic eyedropper.

As for paintbrushes, get natural bristle, wooden unpainted hanldes and you'll have no problem.

[Wendell Ricketts]

If you want the true technical details, you can have a look at this chart: http://www.vp-scientific.com/Chemical_Resistance_Chart.htm. The same chemist friend who pointed me to the chart said that the state of the art are PTFE plastics, though I have no idea how accessible those are to the general public. In any case, it won't be hard to find something to hold your Butvar mixture. I actually switched over not long ago to B98, which dissolves in alcohol, in order to leave the acetone issue behind for good!

[hoffy]

If you look on the bottom of most plastic containers excluding soda look for HDPE or LD PE . HDPE will be fine with acetone. HD. Is high density LD is low density. Most cleaners will be in HD bottle. Hope this helps y

ou out.

[BisonJim]

Thanks to every one for all the help. I did use natural bristles and a glass jar, one quart acetone with about fifteen teaspoons of Butvar B-76 after 24 hours to mix. Lesson learned: For *MY* particular application and "*MY* chalky old bison skulls, the ideal would have been a large tub full of the stuff, dunk them in for total immersion for about ten minutes (or longer?) and then take them out to dry.

I only got through two skulls and it they were soaking it up FAST and it was drying FAST. So fast that I'm not really sure how deep the mixture got into the bone. All those nasal structures and sponge-like sinus struts, etc. were hard to get to and I know my job was not complete. Plus, the brush was knocking some tiny pieces of bone off. Good thing these skulls are not real valuable. Maybe the alternative product with alcohol would be better but I did like the "liquidy", non-oily sense of soaking I got with the acetone. I was outside in the wind so maybe that contributed to the sense of drying too fast.

Someone said I should apply maybe a coat or two with a brush before dunking. I think that is a good idea. Now I have them hard enough to handle the dunking and I'll probably get around to finishing the project someday. True fossils and wood and other projects are probably different.

Again, thanks for the help.

[Harry Pristis]

This question comes up repeatedly. Here is a thread with info on techniqes for using Butvar B-76 and other consolidants: http://www.thefossil...e__hl__acryloid

It is important that the granules of B-76 be sprinkled into the acetone so that they have an extended opportunity to dissolve. Failure to slowly drizzle the granules will result in a resistant layer of plastic on the bottom of the container.

I always use a glass jar for dissolving the B-76 so that I can see the progress of my work (and this is work!). I shake the solution so that it is violently agitated. Finally, the solution is ready when there is no big clump of jell-like plastic on the bottom and when the tiniest air bubbles are slightly retarded in their rise to the surface.

You don't "paint" or "coat" bone with B-76. You soak the bone to impregnate it with the solution. Use a turkey baster on the larger bones (like a bison skull). Squirt the consolidant into all the foramina you see. Baste the bone until you see no air bubbles emerging.

Large, acetone-resistant plastic tubs are available at Target where they are sold as "storage boxes." What you want is the flexible, RubberMaid or Tupperware sort of plastic.

Butvar B-76 is soluble in alcohol as well as acetone. Acetone is nasty stuff, but I've never tried alcohol as a solvent.

[Barby]

This is all good input! 

Thanks,all!

I'm sticking with my B-98 for field work, but i want to try the suggestion to mix  the B-76 with alcohol, to see how I like the effect.

Here's what I do for field work: I mix B-98 in a gallon can of acetone,(after drawing off a small amount of acetone to make room for the powder).I add a bit more B-98 than recommended , as it's easier to thin a small batch than to thicken it.

The best container to carry for field work is -believe it or not-- a Gatorade "squirt bottle" , the kind with the twist lid with the little hole at the top. (i can usually find them at gas stations). I grease both the inside of the lid, and the "screw" part on the bottle with Vaseline, so i can get the top off easily for refills. These bottles squirt the butvar where ever  I want it-- I can use a cheap disposable  brush to spread it, if necessary. These Gatorade bottles can be used for a couple of years.They "suck in" a bit between uses, but pop back out with refills.

Also, they fit perfectly in the backpack slot designed for drink bottles.