Q: holes in borosilicate tubing

Hi Mark,

To do it as you describe, you use tungston wire.

But what you need is called a "frit" It is much like a fuel filter. It is made of borosilicate glass. It passes liquid or gas. It comes in different porosity ranges. From extra fine to extra coarse. Here is an example of fritted disks that are available.

also have them already sealed to a tube. that helps.

Randy Hansen SC Glass Tech Scam Diego, Comi-fornia

Purpose of the air is.....? Agitation of solution?

CRL sells very ting diamond bits, which could be a mechanical solution, very tight, high temp torch fire would do it, but be very aggravating to do an "lot" of tiny holes, and how big is TOO big? If the purpose is agitation, why not lower air pressure and only 3 or 4 holes, that would be easily do-able. But the container is how big?

Indeed David, that may be the best way to go, both in simplicity and cost. MegaUK comes highly recommended, I heard about them from

- the Americas distributor is Randy's idea of using fritted glass is a nice one, but it looks like the fritted elements only come in a disc form. This could work if the design were altered to include a separate cylindrical bubble chamber. It's still in the concept phase so anything is possible.

Javahut, the tank will be a thin box, about a foot square and standing on its edge. the air bubbling serves to regenerate the etching solution. Apparently agitation is not necessary. As copper from the board is disolved, the solution gains Cu+ ions which are inert. To convert those to the active Cu++ ions, air is bubbled through the solution. Oxygen and some HCL is consumed to regenerate the etchant. No waste = environmentally friendly. (Cupric chloride is nasty stuff to dispose of however, any excess etchant must be chemically neutralized.) No such thing as a free lunch. :)

Regards, Mark

the fritted elements only come in a disc form. This could work if the design were altered to include a separate cylindrical bubble chamber. It's still in the concept phase so anything is possible.

Indeed I'll try the air stone idea, they are cheap and make nice bubbles. I just hope the stone isn't alkaline in composition.

Cupric chloride etchant isn't new, I hear that many commercial PCB makers use it. The interesting thing about CuCl is that there is no waste - just bubble the solution and maintain acidity to keep it working. It also etches quickly and over a wide temperature range. The downsides are that HCl is consumed and the by-product of regeneration is more etchant. It is toxic, but excess can be sold to industry or neutralized easily- just add magnesium metal. The end result is solid copper precipitate, which can be recycled.

Alternately, adding sodium hydroxide to the etchant creates copper hydroxide (blue crystals) and table salt. Cu(OH)2 is an inorganic bactericide and fungicide. This could also be heated to make copper oxide, which is used in pottery making... Oh sorry, this is straying far from glassworking. :)

-M