Help with CA glue not bonding oak on oak

[Rob444]

I have been experimenting with the Paranoid B-72 that can apparently be used as an adhesive or a clear seal.


I mixed it (by weight) to a 25% solution in acetone. It can also apparently be resolved in alcohols. It resolves in acetone very slowly. I let it dissolve overnight. In the morning it was a viscous transparent layer on the bottom of the acetone that you could discern because of the different index of refraction. I had to shake it vigoursly for several minutes to get it to mix evenly with the acetone.

I tried it to attach line to some blocks and gluing two pieces of wood together.



The acetone evaporates very quickly. even after clamping the wood together there was no real adhesion between the parts. The line stuck to the block, but I would say much less than if I used PVA glue. I will try using more between the wood pieces to see what happens.

I also bought the suggested fumed silica to mix with it. This is supposed to improve the viscosity and adhesive properties. The silica is an extremely fine dust. It will probably be hard to mix evenly and I will be using my paint hood and a respirator mask before I take it out of the container. I recommend that anyone else who wishes to to experiment with the silica do the same to protect their lungs.



I'll report back in a few days with the results. If I am unhappy with it I will try desolving it in alcohol.

Rob

 

[Pepite 1/60]

Why do poeple insist poisening themselves uselessly?

https://www.highlandwoodworking.com/library/using_hide_glue.pdf

 

[Bob Cleek]

The difficulties you've reported may be related to your preparation and handling methods. For proper mixing and thickening see: https://resources.culturalheritage....ontent/uploads/sites/8/2021/11/osg025-001.pdf

The method of mixing the B72 pellets and the acetone is determinative of the initial thickness of the mixed suspension according to various instructional videos online. (Always to be taken with a grain of salt.) They say that allowing a bag of pellets suspended at the top of the container of solvent to dissolve overnight and fall slowly through the column of solvent, will yield a thicker, and more uniformly dissolved suspension for adhesive applications. Shaking the mixture to more evenly suspend the resin in the solvent is not advised due to issues with air entrapment (bubbles) and the natural slow dissolving properties of the material in the solvent. (Which I presume is science-speak for "Just shaking the stuff doesn't do much good.")

From what I gather, B72 does not like to be mixed forcefully, but rather to "drift down" through the solvent column to create an evenly distributed suspension. If the suspension isn't evenly distributed, the thin material at the top of the container is going to have a different consistency, and therefore different adhesive behavior, than the material that has settled at the bottom oof the container.

This is all from my study. I've yet to get my hands on any of this stuff. So don't take my word for it. As always, "follow the directions on the container." (And online tutorials, as well.)

As for the fumed silica ("Cab-o-sil") I've used plenty of it to thicken various epoxy adhesive and coating materials. Wearing a particulate mask is advisable when mixing. Running a fan in the area is not advisable. Any airflow will blow the stuff all over the place. (Guys in the boatyards call it "pixie dust." ) It's a good all-purpose thickener but when using it to thicken an adhesive, remember that while the silica powder thickens the resin, it does not add any adhesive properties. It will add some structural strength to the adhesive matrix, but it is not "sticky," so realize that a thin solution of B 72, as mixed for use as a sealer or coating, when thickened with silica will not increase the adhesive strength of the thin B 72 mixture.

Watching your reports closely!

 

[Rob444]

I carefully mixed about 1/2 a teaspoon of the fumed silica with the B-72. As Bob Cleek mentioned the stuff is amazingly fluffy. It makes dust look heavy. I mixed it and allowed to to dissolve for several days, mixing occasionally. Most of it appears to have finally mixed. The solution is noticeably more viscous and certainly dries slower. However as Mr. Cleek has mentioned it has not increased the adhesive properties of the B 72. It does seem to make a good sealer for the wood and it definitely can stiffen lines, like CA can, to make threading lines easier. As an adhesive though I have to say I am less than pleased. Hopefully others will experiment with it.

Rob

 

[Bob Cleek]

As an adhesive though I have to say I am less than pleased. Hopefully others will experiment with it.

I plan to experiment with B-72 in the near future. Rob Napier in his Caring for Ship Models book on restoration processes speaks highly of it repeatedly as both a sealer and an adhesive. Conservators love it because they find it very versatile and easily reversable. In my reading up on it, there are two things which contribute to the viscosity, drying time, and adhesive "aggressiveness." The first in the concentration of the pellets in the acetone. The second is the consistency of the suspension of the dissolved B-72 in acetone. The instructions I've read call for placing the pellets in a cheesecloth bag which is suspended over the acetone with just the bottom of the bag touching the acetone. The container is capped and left to sit still overnight. This method causes the B-72 pellets to dissolve slowly and the dissolved B-72 to slowly disperse by the operation of gravity so as to be evenly suspended in the acetone. The suspension is to be "stirred, not shaken" (to avoid air bubble entrapment) and, apparently, it takes more stirring than one would expect to distribute the dissolved B-72 in the acetone. It sounds like it's pretty thick stuff.

Mixing the silica into a syrupy material is pain, given the "fluffiness" of the silica. The silica doesn't "dissolve." It's simply very fine glass dust. It has to be mixed into whatever it's added to. When I want to mix it into a batch of epoxy resin, I've found that it's easier to mix the silica into a small amount acetone and then pour the acetone into the epoxy. The acetone thins the epoxy a bit, depending how much you pour in, but makes it easy to stir the silica into the resin without it clumpin up as it wants to do. The acetone evaporates quickly, leaving the silica evenly suspended in the epoxy resin. I'd suggest trying the same trick with B-72 mixing. It's basically a trick I learned to use when mixing flour into a hot liquid to thicken gravy.

If your B-72 mixture is too thin, the literature I've read says there's no problem with simply adding more B-72 to the thin mixture to thicken it.

 

[Schiffsmodellbauer]

I noticed that coating, even minuscule amounts of CA, makes the lines pretty brittle. They have often break when trying to move some lines while building the HMS Endeavor.

 

[Bob Cleek]

As Bob Cleek mentioned the stuff is amazingly fluffy. It makes dust look heavy.

I usually take materials safety warnings with a grain of salt... or whatever. I live in California, "The Land of Fruits and Nuts," and we've got statutory "cancer warnings" printed on just about everything we buy here, but the more I thought about it, the more I felt I really needed to add a caution to my previous post.

Fumed silica, or "Cab-O-Sil" by one brand name, which is basically very, very fine silica (AKA: "glass") particles, while not toxic if ingested by mouth, can cause silicosis if inhaled in sufficient quantities "all at once" or over a long period of time. Siilicosis is a lung disease that can develop from breathing in silica dust, usually around mining and construction sites, and, in this instance, when working with it in the form of fumed silica additive for thickening resin adhesives. Symptoms include a long-lasting cough, problems breathing, inflammation in your airways and scarring in your lung tissue. These symptoms can lead ultimately to nasty things like lupus and other autoimmune diseases, chronic kidney disease, and lung cancer. There are no cures and the damage is irreversible. (See: https://my.clevelandclinic.org/health/diseases/22622-silicosis) (While the mechanics of developing silicosis and asbestosis are the same, the substances causing each, silica and asbestos dusts, are different and the resulting lung diseases are identifiably distinct from one another.)

In this case, I'd urge anybody using fumed silica additive to handle it carefully so it doesn't blow all over your workspace, vacuum up any spillage well, making sure your vacuum system exhaust doesn't just blow back out all over your shop, and wear a good particulate PPE mask.