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Technical questions on etching and annealing
another possibility might be that the rougher sides caused more air
pockets/bubbles in the etching medium so didn't etch as completely. when i etch i always 'work' the acid to alleviate this problem.?? m "Terry Harper" wrote in message ... "D Brock" wrote in message ... 1. Is it generally true that opaque glasses etch more easily/evenly than transparent glasses? As opal glasses have a second phase which is crystalline, it can well be that this is more easily attacked by the etchant than is the body glass. There are two main types, fluoride and phosphate opals. -- Terry Harper http://www.terry.harper.btinternet.co.uk/ |
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"Michele Blank" wrote in message ... another possibility might be that the rougher sides caused more air pockets/bubbles in the etching medium so didn't etch as completely. when i etch i always 'work' the acid to alleviate this problem.?? m "Terry Harper" wrote in message ... "D Brock" wrote in message ... 1. Is it generally true that opaque glasses etch more easily/evenly than transparent glasses? As opal glasses have a second phase which is crystalline, it can well be that this is more easily attacked by the etchant than is the body glass. There are two main types, fluoride and phosphate opals. -- Terry Harper http://www.terry.harper.btinternet.co.uk/ That does indeed help. Another thing to watch is the cleanliness of item to be etched. Make sure there is no grease residue or handling residue [from hands/fingers] etc...it can act as a 'block' to the etching. Kitty |
#3
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All:
Thanks for the comments. Just for the record --- yeah, I'm very careful with this stuff. I actually have (back in university days) used HF acid to do glass etching (non-artistic), was quite rightly paranoid/careful with the stuff. It's nasty. I'm pretty sure that the effects I'm seeing are not related to either the glass being dirty at start, or to pieces touching each other or the sides of the container. From the responses I'm getting here and other places, it seems like my thoughts about different annealing states affecting the etching properties are at least plausible... Thanks for the responses --- and other people's thoughts and observations are still quite welcome! I'm still watching! --Dave "Louis Cage" wrote in message ... Transparent glasses seem to be a bit "stiffer" than opaque ones, so that may have something to do with your cracking problem because they would reach the "solid" stage quicker than opals. This would trap more heat inside the bead and also the outer layer would shrink faster. Etching creams and liquids are salts of hydrofluoric acid (which in its pure form is HIGHLY DANGEROUS - I have been told it is just under Plutonium on the EPA's "nasty chemicals" list). Since they are salts they are not very dangerous, but wear gloves and ventilate the area nonetheless. Hydrofluoric acid etches glass because it dissolves calcium. Probably the opaque colors have more calcium in them to give them opacity. Soft glass, such as Moretti, is also known as soda-lime glass. The acid or cream dissolve the calcium in the lime part of the glass formula. Borosilicate glass uses Boron instead of soda and lime as a fluxing agent and has no calcium. That is why you can't etch Pyrex with these creams. Even if the glass is very clean, you may still get an uneven etch. More so with the cream than the liquid. I think (but do not know for sure) this is caused by the salts being unevenly dissolved in the carrier solution. So stirring the stuff up before you etch the beads may help. The reason Hydrofluoric acid, and to a lesser extent the salts, is dangerous is because it will dissolve the calcium in your body (you bones, teeth, whites of your eyes, etc.). Also if you spill some on you, it doesn't affect your nerves, so you may not feel it. Also the acid boils at room temperature and the vapors are very harmful as well. SO BE SURE AND WEAR GLOVES AND GOGGLES WHEN YOU WORK WITH THIS STUFF, EVEN THE CREAM. -- There are no mistakes, only unexplored techniques "D Brock" wrote in message ... Hi --- I tried out etching some lampwork soft glass (Effetre) beads for the first time, noticed some curious things. Since this was my first go, I used some old beads from my broken beads jar --- ones that cracked or broke during cooling (in heated vermiculite) and were not annealed. I was using Dip 'n' Etch liquid. I noticed that the opaque beads seemed to etch to a nice matte finish much as expected. However, I noticed that transparent colors etched with more difficulty (had to leave in solution longer) and much less evenly. Some surfaces etched nicely, some etched only in little spots or blotches, and some parts did not etch at all. In particular, on one of these transparent beads, was that the main surface of the bead (that was probably worked thouroughly in the flame and also cooled slowest) etched nicely, but the one finished edge (that probably did not get worked so thoroughly in the flame) and the other broken end (which, being broken, may also be telling me that it was not worked enough in the flame) hardly etched at all. Then, looking back into my jar of broken beads, I realized that there were a disproportionate number of transparent beads, few opaque beads. So, three inter-related questions a 1. Is it generally true that opaque glasses etch more easily/evenly than transparent glasses? 2. Is it generally true that opaque glasses are more robust in terms of resisting cooling shock and/or easily annealing 3. Does the annealing state of glass affect its etching characteristics (poorly annealed = etch resistant, well annealed = etchable)? Thanks, --Dave |
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