Scavo for Boro?

[Glass Grimoire]

Ok a little backround for my question, i've been making Hollow Boro Geodes, and other geological samples and i am trying to find a way to create a scavo(ancient looking) finish compatible with boro. The traditional trick for soft glass is a combination of baking soda and some other stuff. The principle i think is that the baking soda is caustic at high tep and eats away at the glass leaving an aged look. But it won't work for boro, while i got the perfect look i wanted it also gave me extreme spiderweb cracking on the surface. so now i'm back to the drawing board and need a new scavo recipie, any ideas out there?

Oh and as a point of reference here is a photo of the most recent attempt look at the rock that is the base, i know you can't see the fractures in this shot there just to small

[BlueLilyStudio]

you'll want to start experimenting with exotic powders and reductive frits like Amazon Bronze, and then focus on the crystal building reduction atmosphere that causes a buildup of silver beads. Then you could experiment with carving with sandblaster instead of baking soda. Or use electroplating to get an antique look. My main concern with the design is checking caused by the acute angles located inside the geode...

[CitizenNot]

^^^^This is why this place rocks!

[Zed]

Scavo is a lot more toxic then baking soda. Some kind of acid powder. I'll look it up.

[Zed]

Actually not that bad. I'd be surprised if this worked at all on boros, but heres a how-to page for scavo-ing soft glass beads.

http://www.anndavisstudio.com/articles/Scavo/

So you applied your formula on boros and heat activated it the same way but it caused spiderweb cracks? Is the scavo definitely the reason?

Did you clean off the scavo before putting the piece in the kiln or after and did you use the kiln or the torch to activate the scavo?

I wouldn't have thought scavo would work at all on boros, learn something new every day I guess.

[richsantaclaus]

I tried Scavo on soft glass and it made more fumes and mess than it was worth. I have the same link and the person makes it look easy to work with - reality is, it isn't!

[Glass Grimoire]

Excellent. Great responses, I did't want to get to deep right away, i wasn't shure if help could be found.

So first to clear up a few things. My "Poor Mans Scavo" Did fail entirly as a scavo, Borosilicate being a chemically resistant glass it had a low probability from the get go.

What it did do was cook into somthing more reminicent to a glaze (This is where the surface only siper web fractures did occur) The look i acheived had nothing to do with "ageing" the glass but was instead mearly an aged looking coating of burnt baking soda. Looks great but non functional and had cracking issues.

With regards to the connections of the crystals on the interior of the geode. First while you are correct about the stress created by acute angles the construction is clean and i have no cracking problems with the geodes themselves(the coldworking reveals interior conections which are clean) and the minerals get fully embeded (think iceburg). I've been using silicon, tektites, moldivite, Kyanite, and even gilson opals, all with no trouble. Even the coldworked crystals on the side of the geode are tektites.

But back to the main question, so i have seen and done the types of finishes you can get through frits and powders and am still looking for somthing more natural looking. Sandblasting may still have some possibilities but it can only get me the texture and the matte finish i want not the crusty old stone look. What i would really like is some king of "super Scavo" A scavo strong enough (or formulated differently enough for boro) to create a similar look to a traditional scavo. that acctually works on boro. What chemical is nasty enough (that won't kill me), that can work on boro

[Zed]

Could you link some of your geodes? they sound cool.

I'd 2nd whoever said that exotic powders/frits might be the way to go to achieve the look I think your talking about. Check out Steve Sizelove's site, his "artifact vessels" might be inspirational.

http://stevesizelove.com

[ALIEN!]

Sandblasting dude. Check out some of the stuff on Robert Mickleson's website. Salt does some nice texturing too, though I think he does some stuff where you dont fully melt "in" the top layer of powder or frit. He has a nice gallery on glasspipes.org.

[Johan]

I would coat it with multiple layers of different size frits and powders, but dont melt them all the way smooth and then sandblast. Maybe try a reduction color like caramel.

[Robert Mickelsen]

Actually, scavo is a base substance, like lye, not acid, but corrosive just the same. And baking soda will work on boro. You just have to get it hot enough to scar the surface. The real trick is getting the reaction to stop once it is started. Wear gloves when handling after cool. Dirty stuff. Leaves nasty (or wonderful, depending on taste) surface pitting. Similar effects cannot be achieved any other way. You will probably have to wash the finished piece and then seal it some way to preserve the effect.

Experiment. Good luck.

- RAM

[Conchis]

I wonder if you heat the piece then roll it in frit of an incompatible glass frit.... let that cool.... get all sorts of fractures and then fire polish it a bit...or not....

[Aymie]

The floor around my bench is covered in those shock absorbing mats from Home Depot...set of four for twenty bucks. The cheap kind that fit together like kids ABC tiles. I dropped a marble once, and when I tried to cook the melted mat off the marble, it had a reaction just like baking soda on soft glass. Any other plastic has melted off fine and dandy...whatever my mat is made of reacted very quickly with the glass. I have been very curious to find out what it is...and also tempted to roll shit on my mat on purpose to get that effect on purpose. May be worth researching what the heck those mats are made of...may be worth buying a set and rolling stuff on them, provided you have good ventilation.

[Mecha]

Hydrofluoric acid eats boro.

I am not sure if it would give you the exact look you are seeking though. I have only used it to etch clear boro and quartz.

It is extremely dangerous to work with, so do your homework before trying it out.

Oh yeah, plus one on posting pics. These sound interesting to say the least!

Good luck!

[Zed]

Better be sure you know what your doing. I'll use silver nitrate but I wouldn't go near full strength hydrofluoric. Quote from wikipedia.

Hydrofluoric acid is extremely corrosive and a contact poison. It should be handled with extreme care, beyond that accorded to other mineral acids, in part because of its low dissociation constant, which allows HF to penetrate tissue more quickly. Symptoms of exposure to hydrofluoric acid may not be immediately evident. HF interferes with nerve function and burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.[7] HF is known to etch bone, and since it penetrates the skin it can weaken bones without destroying the skin.[8] More seriously, it can be absorbed into blood through skin and react with blood calcium, causing cardiac arrest. Burns with areas larger than 25 square inches (160 cm2) have the potential to cause serious systemic toxicity from interference with calcium blood and tissue levels.

Mecha what was your process for using it?

[Mecha]

Better be sure you know what your doing. I'll use silver nitrate but I wouldn't go near full strength hydrofluoric. Quote from wikipedia.




Mecha what was your process for using it?

We used it in the scientific shop to clean quartz and pyrex or etch it for really specific tolerances.

Our solution was 49% and was contained under a chemical hood. We wore full length rubber gloves, face masks with properly rated cartridges, goggles and rubber aprons. There was a full solution tub (49 percent), a low solution tub (around 10 percent) and a rinsing tub with just water. This was all next to a sink fitted with an emergency eye wash station and there was an exposure kit located within arms reach.

The stuff is not to be taken lightly, to be sure. Hence the reason I said do your homework. Get the msds for it and look into the OSHA standards for handling and disposal.

[Aussie]

yeah, hydrofluoric is nasty, I got a tiny tiny bit under my fingernail once and I ended up with a nice hole under the nail ... not to mention the heat and the pain once it got through to a nerve ... also hydrofluoric will polish your glass rather than matten it. we used to use it to take off the etched labels from scientific flasks and such.

sodium carbonate (baking soda) may not be the stuff you're looking for, hence the checking. the flux in borosilicate is boron or boric acid. you can get it in the form of a powder at the local chemist or hardware store and it's used for cleaning drains. when I make my own colours I usually put in a little bit of borax to compensate for the COE change from the oxides and make the glass flow better, which brings me to another suggestion. you may want to hit your local pottery supplier and check out some of the oxides they have. stay away from chromium or cadmium, they're a couple of the really nasty ones and make sure you have really good ventilation when you do this. to get an effect which made the glass look like it's been buried for ages make a solution from a little bit of clear light machine oil or linseed oil combined with a pinch of borax and some oxide. silver oxide is a good one to use if you want a yellowy scabby effect, iron oxide and copper oxide give earthy brown and green tinged effects, cobaltous oxide gives anything from a gunmetal skin to flecked blue. the solution should be mixed to about a tooth paste consistency to apply to the glass without it running off, warm glass is best (I heat it up in the flame before applying the oxide solution. Using a fire resistant cloth (like fiberglass cloth) dab the solution onto the glass. the oil will heat up too quickly to cause thermal shock and cracking (that's why you don't use a water mix). put your coated piece back into a fairly benign flame and watch what happens. you can also try an aggressive flame, but often the oxide will just fly off instead of baking into the surface first.
another idea would be to play around with ceramic onglazes.
some more ... shake some dust out of your vaccuum cleaner's bag and roll the glass around in it, a light coating of concrete dust will also give you a nice scabby look after flaming it in.

just some ideas ... I used to play around a lot like that 20 years ago ...

I can't stress enough the need for good ventilation, though ... be safe

[richsantaclaus]

The bases up in the 13/14 pH range will burn you more than the strongest acids in the 1/2 pH range - PLEASE, this is not kid's stuff - SAFETY FIRST!!!!!

[J Howard]

salt does some nasty stuff.... if you melt enough on, it changes the COE a little on the surface, and will give you some crazing and all out nastiness you might be seeking

[Ro's Glass World]

what about a rough electroform?
ro