Using nitric acid....

[Floorkasp]

I know that in the 1900's, lampworking in Venice and France was sometimes not done on a mandrel with bead release, but straight onto copper. The copper would then be dissolved in nitric acid.

The safety precautions to do this would be extensive, but I was wondering if anyone has tried this. I have come up with a bead design, but the beads are pretty impossible to remove from the mandrel. Too many weak spots to withstand the pressure that comes with removing it.

So I thought it might be an option to use this method. (A long shot, I know...)

[rnmcginnis]

Nitric acid is corrosive and fairly dangerous. If you decide to proceed, I would not use concentrated nitric acid. Use a 50% concentration solution at most. Make certain to use good ventilation. Nitric acid reacts with copper to form copper nitrate (dissolves the copper away) and nitric oxide gas which is irritating and toxic to breathe.
Also, wear gloves and safety glasses. Nitric acid is very corrosive to skin - it turns skin into dull yellow leather on contact.

The waste liquid from the process will contain high concentrations of copper (toxic to fish and other aquatic organisms) and will still be acid. The acid can be neutralized by slowly adding baking soda or sodium hydroxide (lye). It will get warm and may splatter. Baking soda will bubble and foam.

Roger - (chemist in my day job)

[yellowbird]

I think "they" send the mandrels to someone to have the beads removed.


try a bead release that doesn't hold as well.

[losthelm]

Would a long period of time in an electroerch setup accomplish the same thing?
I would think it posible as long as you maintain the circuit through the mandrel.

I know one of the vendors was useing tungsten mandrels to make beads without release.
I'm not sure how it would work with huge beads but its another avenue to explore.

[Holly]

You'll want to use ferric chloride for this purpose. Used properly its pretty safe.

[Speedslug]

Makes me think of a youtube video I saw about making bearings for very old locomotives. The name will come to me while I am trying to sleep of course and not right now when I want it to.

It's the method of melting tin or another soft metal around the axle.

They used the smoke from an acetylene torch to form a pure carbon coating on the axle before pouring the molten metal into the surrounding support with clay dams to keep it from running out the edges.

BRB

It is called "Babbitt" bearings.

Any who, they used a torch without oxygen to create a thick layer of carbon soot on the axle before pouring the "Babbitt" in to the form.

I wonder if that layer of carbon would work in glass as a bead release.

[KJohn]

Perhaps using a hollow tube for a mandrel, and leaving it in place? Trimming the ends, might not be that noticeable, and might also help reinforce the strength of the design.

[bob]

This may be a stupid thought, A wooden skewer dipped in bead release. I might have to try this.
Bob

[glassmaker]

Originally Posted by Floorkasp

I know that in the 1900's, lampworking in Venice and France was sometimes not done on a mandrel with bead release, but straight onto copper. The copper would then be dissolved in nitric acid.

The safety precautions to do this would be extensive, but I was wondering if anyone has tried this. I have come up with a bead design, but the beads are pretty impossible to remove from the mandrel. Too many weak spots to withstand the pressure that comes with removing it.

So I thought it might be an option to use this method. (A long shot, I know...)

I tried it many, many years ago when I had access to a laboratory chemical fume hood and as many nasty acids as I needed. Believe me, it isn't worth the trouble. Not to mention that nitric acid is one of those items the feds frown upon "regular people" having access to since 9/11.

I would suggest coming up with a different solution, perhaps a tungsten mandrel that you can remove by heating? If you insist on pursuing the copper/acid, use tubing for a mandrel instead of wire. There will be a much larger surface area for the acid to attack. But I still strongly discourage it.

Brad

P.S. If you still plan on dissolving out the copper, Holly's suggestion of ferric chloride might be better a better plan than using nitric acid. (Although I don't have any experience with it myself.)

[Chewy2420]

Mmcginnis I would not recommend adding lye into an acid sloution , at best your likely to end up with a volcano effect hurting your self. If that's all you have they I would strongly advise you go outside and dilute the acid down by adding twice as much liquid as the acid solution then add a solution of lye and water ( just a small amount of lye) and add it slowly. After that you can make a stronger and stronger lye solution till you get a pH of 7 . I hope this helps stay safe and wear protective clothing and googles or a face shield

[Sigulf]

I've made beads on copper wire, then annealed then placed in a muratic acid / hydrogen peroxide mix (50/50). Muratic acid can be found in hardware stores for concrete work or pools and hydrogen peroxide at a beauty store supply shop-- much stronger than what you can buy in the cosmetics section. It took a day or so to eat out the wire-- KJohn's suggestion of making the bead on copper tubing is great, it's what I'll do the next time.

[allicat]

As a completely useless aside, I was behind a car today who's license plate read HNO3...

[Floorkasp]

Thanks everyone! Lots of great advice. I actually have nitric acid, as I used it before to etch silver. Was quite surprised that I could just buy it at a drugstore. For now, I have looked at the forum for some other ways to get beads off a mandrel, and I will give the rivet tool suggested somewhere a go on my next set of beads. I tried it on some plain beads that had gotten stuck for some reason, and it worked on half of those. The other half cracked, probably were already broken or had cracked bead release.

[rnmcginnis]

Jeff;
Good point on diluting the acid and using a dilute lye solution before neutralizing to reduce the chance of boiling and splattering.

[hyperT]

Originally Posted by Floorkasp

I know that in the 1900's, lampworking in Venice and France was sometimes not done on a mandrel with bead release, but straight onto copper. The copper would then be dissolved in nitric acid.

The safety precautions to do this would be extensive, but I was wondering if anyone has tried this. I have come up with a bead design, but the beads are pretty impossible to remove from the mandrel. Too many weak spots to withstand the pressure that comes with removing it.

So I thought it might be an option to use this method. (A long shot, I know...)

Years ago I would make beads on a copper wire pulled tight in my glass lathe. 4 ft long. The beads were flame annealed with a fisher burner, which I moved along as they were made. After I had a bunch made and they were cooled down. I would put one end of the strand into a vise and simply stretch the wire, the beads would slide right off. No bead release was used at all.

[Isabelle72]

I've tried copper wire when I was in Murano(it still largely used to make glass beads in Venice) and it's true that it may be very useful to make some banana/leaf etc. shape, and also if you work with transparent colors.Then my beads was sent to a factory to remove the copper. I think is highly recommendable to not use nitric acid at home. It's better for us and also for the environment

[hyperT]

Always add acid to water. Never add water to acid. Adding water to acid can cause a rather violent reaction!