[femto]

Below is a table of elements used, ordered by boiling point. Beryllium has the lowest boiling point at 2742K. Zirconium has the highest melting point at 2125K. This means the furnace temperature was greater than 2125K.

TIG temperature can easily reach 3000C (close enough to 3000K) [1], more than the boiling point of beryllium. The temperature of the metal slug would rise until it reaches thermal equilibrium through heat loss, the energy loss likely being due to the vapourisation of the element with the lowest boiling point: beryllium.

That smoke was probably beryllium vapour.

I'm no expert, but I would assume the beryllium vapour would not have made it out of the apparatus. By luck, it would have condensed either before reaching the HEPA filter or on its way through the HEPA filter, even though the HEPA filter was not designed to stop a vapour. Nile Red also had the sense to use a fume cupboard. Despite this, the inside of the apparatus could well have been coated with friable condensed beryllium, which would probably not have been flushed by the argon. If doing this, I'd take additional precautions against condensing beryllium vapour containing the equipment (I don't know what they might be).

Maybe it's a case of controlling arc temperature to keep it below the boiling point of beryllium? Maybe a small amount of impurity with a lower boiling point can be added to the mix, so it boils off first and avoids the beryllium boiling? This might also prevent loss of beryllium from altering the composition of the glass?

How would the pros handle this risk?

I gather there are similar issues with the refining of silicon, in which silicon vapour can cause silicosis.

   Element    Melt   Boil
   Beryllium  1560K  2742K
   Copper     1357K  2835K
   Nickel     1728K  3003K
   Titanium   1491K  3560K
   Zirconium  2125K  4650K

[1] https://hypertextbook.com/facts/2007/AnthonyHo.shtml

[aDyslecticCrow]

That is interesting. That explains why the Beryllium vaporized... I'm surprised Nile didn't mention or consider that.

I think the simplest solution would be to lower the voltage, aim the arc at the Beryllium, and ensure it and the copper, nickel, and titanium melt together before ramping up the voltage to integrate the Zirconium.

[maronato]

Nile mentions that the mass lost during that step is very close to the mass of beryllium impurities.

I’m no chemist, but it’s possible that all these metals together form a eutectic system, meaning you can’t distill the beryllium alone.

[Metacelsus]

There could also have been moisture on the beryllium.