Need help painting glass

[RichardP]

I have Cornwalls which have glossy black glass tops, put there by a previous owner to cover blemishes in the walnut-stained birch. I had to replace a broken piece, which turned out to be plain glass with some sort of hard finish. I have tried to paint a black

finish on it several times now, and none has bonded to the glass. I have tried regular krylon spray paint (didn't stick), sanding the glass before painting (couldn't really rough it up much), paint on top of a primer (primer didn't bond to glass), etching the surface with muriatic acid then primer & paint (no etching really occurred), and acrylic paint for made for artsy glass projects (texture way too thick). I know about some glass paints which are self-leveling, and some made to be oven-hardened, but unfortunately the glass sheet won't fit in my oven. I would have to order these online, without knowing if they would work. Is there someone who knows paint, especially specialty paints for glass, who could give me some advice or suggestions? (I am looking in your direction, Michael Hurd ) Thanks in advance for any assistance.

[michael hurd]

Muriatic acid will not etch glass. You need hydroflouric acid. Not hydrochloric acid. Very very dangerous stuff, you only need a small quantity to etch glass. You may also visit a glass shop, and see if they can etch it for you, without the need to handle it.

I used diluted hydrofloric acid in grade 12 science to etch a pattern on a sheet of glass, that was coated with a very thick layer of wax. You simply had to carve out a pattern in the wax with an exact-o knife and then apply the acid.

[RichardP]

Michael, given that the etching option seems dangerous and unpleasant, is there any other way to get a semi-hard coating (black, glossy) onto the glass? Obviously, a previous owner of my speakers did so, but I don't know who that was. The coating does not have to stand up to abrasion or scratching, as nothing will be placed on the speaker top, but it will have to be hard enough not to rub off with light fingernail pressure (as all my attempts do now).

Thanks.

[Duke Spinner]

Sandblast, before paint .....

[WMcD]

There is a product out there which is used to allow home made monograms, etc., to be made on drinking glasses. It looks like sand blasting in a can.

I don't know if wet or dry paper will scratch glass. Worth a try.

Amature telescope makers grind mirrors with some compound. Maybe a local telescope club can give you some advice.

I wonder. McIntosh equipment have beautiful black glass front panels. It must be black paint on the reverse side. These sometimes suffer from bubbles, which may be the paint coming off.

Best,

Gil

[sputnik]

Can't you just buy black glass to replace the broken one? Is the "hard finish" an original glaze? You might look into something like an arts and crafts glaze.

an arts and crafts glaze link

Edit: This may not be a permanent glaze and there's probably something better but maybe a product like this could work for you.

[sputnik]

Wait a minute. I just had a brainstorm! Forget about the glass altogether and just glue one of these fine fabrics over your speakers. You'd be the envy of the forum. Chicks really dig this stuff > if ya know what I mean.

[michael hurd]

You could sandblast the glass, but you would want to use aluminum oxide grit, as it is not as aggressive as other options ( slag rejects ). However, I think that the goal here is not to spend a lot of money just to paint the glass black. I would recomend a two-part paint, however it is not a solution for everyone.

A lacquer in a spray can would probably be about the best bet, as far as cost/performance ratio goes. An enamel type paint in a spray can would be shiny, but would not be as hard as a lacquer. At any rate, the glass must be either etched, or blasted to give a good bond. You can also try a wet/dry sandpaper, as suggested by William. It has a much sharper grit than aluminum oxide, flint, or garnet, the latter two designed for sanding wood. Adding a drop of dish soap in the water will allow the sandpaper to glide easier, and cut effectively.

[michael hurd]

My recommendation would be to definatly try to etch/blast the glass if practical, and my instinct would be to purchase an aerosol spraycan of SEM brand trim black, in a gloss finish. They have the same product in a satin finish as well, the gloss is what you are trying to match, so be sure to purchase the right one.

You should be able to purchase this through a supplier that sells automotive refinish supplies, or maybe Pep Boys. ( I live in Canada, we don't have them, so I can't be sure )

http://www.sem.ws/product.php?product_id=132

[Jay481985]

DO NOT USE HYDROFLOURIC ACID IN ANY CASE UNLESS YOU ARE CERTIFIED WITH THE PRODUCT.

That is my warning since I handled 56% hydroflouric acid and know of the dangers. The safety limit is 12 parts per million in the air. Anything more then that is hazardous to your health. If not used under a vent it will burn your lungs and airway. If not wearing gloves and it splashes it will eat your bones. The Flouride bonds with the calcium in your bones making them hollow or weak. Acutally I know of a professor that spilt it and immediately cleaned it with an acid spill kit but that 10 seconds it was on was enough to burn his skin and actually had to have a cast since his forearm bone was so weak. The funny thing is though it is a acid it is really not classified as an acid. The strongest acid is supposedly hydrochloric acid. But hydroflouric is by far the most strongest due to the valence. Also another funny part is that HF will not eat through most plastics but will eat through glass and metals. Its sorta funny seeing all the acids besides HF in glass bottles while the HF is in a plastic bottle that looks like an enlarged visine eyedrop bottle.

[Jay481985]

btw a safety sheet of hyrdoflouric acid can be found here

https://fscimage.fishersci.com/msds/11171.htm

or

http://physchem.ox.ac.uk/MSDS/HY/hydrofluoric_acid.html

or

http://www.soest.hawaii.edu/~khal/chemistry/HF.html

[RichardP]

Thanks, everybody, for the advice and warnings. I will certainly stay away from the hydroflouric acid; despite our usual ravings on this forum, the speaker appearance is not worth such a risk. I am going to give it one more try, with the wet-dry sandpaper and some lacquer paint. If that doesn't work, I think I will just chuck this $7 piece of abused glass and get a piece of dark smoked glass, which is about $20 around here.

[Rockets]

Go here

http://www.dickblick.com/zz029/65/products.asp?param=0&ig_id=6018

I've never used this product, but is probably a weak acid. For two bucks to try, you can't go too far wrong.

BTW, I also etch glass

Good Luck!

[joessportster]

here is a very inexpensive way to etch glass if you already have a small air compressor, i did this a few years ago and it worked great, you dont need a sandblasting set just a small compressor and a cheap version of a mity vac available at most auto parts stores, use the cup provided with the tool and put some playground sand in it hook one side of the cap for the bottle to your air gun, and hook a short piece of hose to the other side of the cap, and you havew a small inexpensive sand blaster that can also be used to bleed brakes check vacume on engines etc... sounds crazy i know but it works Joe