Does anyone know at what temperature diamonds will frost? I want to anneal a silver bracelet that has diamonds in it.
I do not understand.
A diamond is already a solid so it are already āfrozenā.
In my understanding is that when you frost something,
you make it unclear by etching or grinding and that is not what you want is it?
Itās called smoking a diamond. Itās important to slather the stones with a mixture of boric acid and denatured alcohol first. That said never ever do the boric and alcohol to rubies or sapphires. You should be able to anneal silver without harming the diamonds. To be safe, turn the lights off or down while annealing so that you can see the metal color change easier. Also do NOT quench the piece. Let it air cool.
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When you get a diamond to hot it can get a white haze on the surface that wonāt come off unless it is re-polished.
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I was thinking of doing it in a kiln where I can set the temperature and get a nice even heat. Thatās why I was asking about the temperature that diamonds smoke.
I have tried to find the answer to this some time ago, but canāt seem to get a number.
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Do that have to do with the quality of the Diamond or that the surface oxidize due to the heat and Oxygen?
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It is due to heating the stone in an oxygen atmosphere. Thatās why a coating of borax glass will protect diamonds in the fire.
However, while diamonds can be put in the fire, they are still susceptible to damage from thermal shock. Never put diamonds in the fire where there is a cool breeze or set the stone on a cool surface while it is still hot. The stress from thermal shock can cause them to crack along a cleavage plane.
When I had to put diamonds in the fire, say for re-tipping prongs (usually on rings), Iād set up the piece on a charcoal block, and when the soldering was done Iād put the block with the ring still set on it into the sweeps tray where it could cool gently away from any stray breezes.
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Thatās what Iāve been taught as well, that a melted boric acid coating is acting as a thermal insulator to help prevent thermal shock (meaning the inside of the stone cooling at a different rate than the outside can lead to thermal shock right?)
Poodlepup3 wants to anneal a silver bracelet in a kiln. Annealing temp for sterling silver is 1100 F. Assuming these are diamonds and not a stone that looks like a diamond. I think thatās a safe temp to heat the diamonds to without damaging them. Do folks agree with that? Iāve never annealed in a kiln. Iām assuming that you still need to coat with boric acid right?
Side note, I checked the forum search engine and there are lots of threads about frosting diamonds, but I didnāt see a temperature of when it happens.
https://orchid.ganoksin.com/search?q=frosting%20a%20diamond
Hereās an interesting thread that I saw about annealing silver that goes way back in time in the forum. Kind of fun to see, Alan Revere chiming in on the topic. One of my concerns about annealing in a kiln was heating too long and heat hardening the metal. This thread talks about that as well.
Itās been a while, but I have frosted small diamonds (never a large one) a couple of times doing jewelry store retipping repairs. The diamond has had to get to a bright red heat, which is hotter than 1100 F, if that helps.
Jeff
Here is the official info from GIA about diamonds and heat. https://www.gia.edu/diamond-care-cleaning
I have found that the only times Iāve ever seen someone āsmokeā a diamond was when they were working with platinum too close to the stone.
And finally I am surprised that someone would make a silver bracelet and set it with diamonds. I would definitely want to make sure that the stones are not CZs, white sapphires, or some other diamond substitute that canāt take the kind of heat that a diamond can.
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The only times I ever frosted small diamonds it was while working in PT with the torch.
Hi,
i found this postā¦
and the one below isnt exactly what you are talking aboutā¦frostingā¦but i thought i would addā¦
I seem to recall, in the back of my brain, something about needing to make sure the diamonds were clean before any heating, or they would getā¦some kinda burned-onā¦discolorationā¦that is / hard/impossible to removeā¦
anyone know if my brain is recalling correctly?ā¦
edit- i found this older post
and this oneā¦on an interesting, kinda related noteā¦
ganoksin archives are priceless!
julie
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Thanks everyone. There is a lot of good information here.
I need to better explain what Iām doing.
Iām not really trying to anneal my silver bracelet I want to get the white surface back from depletion gilding. I want to Keum-boo this piece.
I started out by kneeling and depletion gilding the piece of silver before I hammered it into a cuff bracelet. Then I set the diamonds. Now I want to put Keum-boo it. I need to get that white surface back in order to put the gold foil on. Hindsight is 2020, I messed up. Does anyone have any ideas?
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Sounds like selective metal etching may suit your purposes?
āLikewise, with an appropriate chemical, a layer of nearly pure silver can be produced on an object made of copper and silver. For instance, sterling silver can be depletedāādepletion silveringāāto produce a fine silver surface, perhaps as preamble to application of gold, as in the Keum-boo technique.
(Depletion gilding - Wikipedia)
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Do you know what that appropriate chemical is. The article did not say.
What Iām I reading in this Wikipedia page that is itās describing what folks ordinarily do in preparing sterling for Keum-boo. Repeated cycles of anneal, then pickle to deplete the copper on the surface in sterling alloy.
Iāve been taught, that Sparex pickle is sodium bisulfate and that when sodium bisulfate is added to water it turns into sulfuric acid. Sulfuric acid eats copper, but not silver. When annealing, the silver and copper separate on the surface, which is why silver turns black. (the black is the copper) Youāve probably noticed that after annealing and pickling for a while the silver stays white, meaning the copper is being depleted from the surface, leaving a coating of fine silver.
The article says:
"In depletion gilding, other metals are etched away from the surface of an object composed of a gold alloy by the use of acids or salts, often in combination with heat. Since no gold is added, only an object made of an alloy that already contains gold can be depletion gilded.
Depletion gilding relies on the fact that gold is highly resistant to oxidation or corrosion by most common chemicals, whereas many other metals are not. Depletion gilding is most often used to treat alloys of gold with copper or silver. Unlike gold, both copper and silver readily react with a variety of chemicals. For example, nitric acid is effective as an etching agent for both copper and silver. Under the proper circumstances, even ordinary table salt will react with either metal.
The object to be gilded is coated, immersed, or packed in a suitable acid or salt, and usually heated to speed the process. These chemicals then attack the metallic copper and silver in the objectās surface, transforming it to various copper and silver compounds. The resulting copper and silver compounds can be removed from the objectās surface by a number of processes. Washing, chemical leaching, heating, or even physical absorption by porous materials such as brick dust have all been used historically. Meanwhile, the relatively inert gold is left unaffected. The result is a thin layer of nearly pure gold on the surface of the original object."
I might be wrong here, but Iām pretty sure there isnāt a magic chemical (acid or salt) to deplete the copper from the surface of sterling without heating the sterling to annealing temp first.
Your original question was about what temperature will hurt diamonds. I think all responses so far have said that annealing to 1100 F wonāt hurt diamonds if theyāre first coated with a boric acid mixture.
What I donāt know is if coating your sterling bracelet with boric acid will affect the depletion guiding process? Iāve always done depletion guilding on sterling with it being uncoated. Maybe someone else knows the answer to that.
Forgive me! I have to ask. Can you consider not doing Keum-boo on this piece? It will make your life a lot easier. Or can you unset and reset the stones?
Wish we had some easy answers for you!! Let us know what you decide to do.
Jeff
Thank you so much for your answer, Jeff. Yes, if you coat the sterling with flux, it will not depletion guild. And yes, it would make my life easier not to put the Kim boo on it. But alas, at work Iām being required to. So Iām gonna have to flux the diamonds alone and not the silver and give it a good try.
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Let us know how it works out. Itās a really interesting predicament. Good luck!!
Jeff
diamonds are heat resistant up to 700 degrees C or a bit more than 1200 Fā¦ at those temperatures, surface oxidation in the presence of atmospheric oxygen will start, causing āfrostingā or loss of surface polishā¦ 14K gold will anneal at 1200 Fā¦ or cherry redā¦ Sterling silver anneals at 1100Fā¦ exposure time to oxygen also will make a differenceā¦ if you are anneal sterling aim for a very dull, red temperatureā¦ if using a kiln set at 1100F, do not expose the diamond to any more time than it takes to heat the silver up and remove immediately to air cool. Do NOT quench.,ā¦ natural diamonds have internal stress, evident from stress lines by microscopic examinationā¦ thermal shock can shatter a diamondā¦higher temperatures or longer exposure times to air at high temperatures will cause damage to the diamondā¦ Elliot Nesterman is also absolutely correct to mention that a coating of borax glass which protects the diamond from air. That prevents oxygen in the air from reaching the diamondā¦ the entire diamond should be protected with boric acid or borateā¦ smoking the bottom facets below the girdle will also ruin a diamondās āsparkleā as the internal reflections of light will be absorbed by the smoke surfaceā¦do NOT try from maximum anneal softnessā¦ the temperature is cherry red and too high for safety for a diamondā¦
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this is more theoretical, but also practical-- if depletion guilding is oxidation dependent, borate coatings will exclude oxygen from the air and the process wonāt workā¦ since the original question was about diamonds, trying the do repeated cycles of annealing will not be easy on the diamondā¦ I would not risk more than one anneal on the piece unless the diamond was removedā¦ trying to chemically remove copper with repeated heat/cool cycles will definitely ruin the diamondā¦
you do have a predicament if you have to repeatedly heat and cool the piece while leaving the diamond in itā¦ repeating the cycles of annealing temperature and cooling will eventually oxidize and ruin the diamondā¦ donāt do it more than onceā¦ your best bet is to remove the diamond. donāt flux the silver if this process is what you wantā¦ oxidation of the copper out of the sterling is the process that you are achievingā¦ the goal of protecting the diamond while repeatedly heating and cooling is not possibleā¦ the aims are mutually exclusive.