etching glass ?

[Andrew Gabriel]

Small quantities quickly cause bone destruction. I think it's only a catalyst, so it's not used up in the process and can just cary on going.

Hydrofluoric acid used to be used to make frosted light bulb glass. Glass frosted in this way was very good at diffusing light without generating much loss. It was also possible to etch toughened glass (light bulbs are slightly toughened so they can get away with using very thin glass).

However, even in such carefully controlled industrial processes, handling is now considered too dangerous for this, and they've had to switch to less efficient (in light terms) methods such as powered coatings.

[Huge]

It wasn't a wheel at all. It was a straight stone.

[Andy Dingley]

If they do much of this work, it's likely to be an abrasive belt. This also make it quicker and easier to change abrasives if you're going for a full polish.

[Andy Dingley]

It's not a catalytic reaction, but as you point out it's self-regenerating and so it does carry on until you take action to stop it.

Still is. Hydrofluoric is used to etch, then bifluoric (which leaves a smooth surface) is used to "polish" the etch a little, giving dispersion without much loss.

[Frank Erskine]

Just in "tonight's" local evening rag:-

[Andrew Gabriel]

I'm told it all stopped a couple of years ago, at least for standard light cheap bulbs. I haven't bought any myself for 20 years, but looking at standard bulbs other people buy, they are now just a fine power coating on the inside of the glass. The final straw was aparently being unable to find anyone still willing to dispose of the spent acid at end of use.

[Graham.]

"Colin Wilson" wrote in message news: [e-mail]...

Now that ball mice are largly a thing of the past how come promotional mouse-mats are usually not sutable for optical mice? Many a time I get complaints of jumping cursors, and using a mat-less desk-top provides a complete cure.

[Andrew Gabriel]

which firemen need to be aware of is the fluoroelastomer synthetic rubber used to make things like rubber door seals in cars. In certain specific conditions in a fire, they produce hydrofluoric acid when burned. This presents a nasty hidden danger for anyone handling a vehicle after a fire.

[Andy Burns]

I find that a clean sheet of A4 works best for most optical mice, perhaps promotional mouse-mats could be printed with white ink on a white background?

[The Natural Philosopher]

I use a sheet of black Depron..

[<me9]

Was it 'viton' used for gaskets/O rings that has similar properties in fires? We had to stop using it at work several years ago.

[Chewbacca]

Correct - It's fluorinated rubbers such as viton that decompose at high temperature to produce HF. They are also expensive, so would be very surprised if used for door seals. O rings might be.

Used to work with a guy that had had a tiny drip of HF acid on his hand. He had a hole about 4mm diameter and about 4mm deep in his hand. It had been like that for 20 years. It never closed up....

[Vernon]

Odd, more likely to be phosphoric acid that had burnt the skin, HF generally does not burn (or rather does not give a burning sensation) on contact with skin. It is absorbed into the body, and makes for the bones, HF antidote gel draws the HF to the surface and neutralises it. If not treated it will work through the body, removing the calcium from your bones. If treatment is not forthcoming, you will experience severe pain in the affected bones, treatment at that stage is usually amputation.

[Andy Dingley]

That wouldn't have been HF, as that's almost invisible with skin contact

- one of the hazards of it. It's the calcium in bone that HF goes for. There are plenty of other fluorine compounds that will produce super long-lived ulcers though.

[Graham.]

Not sure if you are taking the p*ss there :-) perhaps using various shades approximating cyan and black would be immune to the red sensitive mouse optics. Maybe the mice would work on more surfaces by using infra-red, I realise the surface needs a slight texture, like paper.