Work hardening hollow domes

[purplepepper8]

Hi,

I'm working on making hollow domes like this

and was wondering if You'll know of any way I can work harden them? These pieces are up to .5mm in thickness so should I go thicker to add more strength or will work hardening work? Dents form in he piece if its dropped and the flat portion also seems prone to bending, although I'm currently using pure silver for prototypes but will be making them in 18k gold.


What would be the best way to keep the inside of the dome clean through the soldering process because I don't know if it can be cleaned once it has been soldered.

Would using a tumbler help with either of, or both of these issues? (I don't currently have one so will have to buy one).

Thanks

 

[monk]

most any metal will get hard with sufficient pounding, gold included. what is the intended application for the domes? i used to make a lot of domes out of copper, brass, annd silver. they were .75" in dia. i found that cleaning the outside as well as a bit on the inside, they wouldd solder together perfectly. i used them to make really dumb looking bracelets. the women liked the bracelets, i liked the money.

 

[purplepepper8]

But because its hollow I can't pound it- it’ll warp/ form dents. The domes are for earrings/ rings. I’ll be engraving on them. And just to clarify the size these are around 0.5 inch in diameter. The soldering isn't the issue- its cleaning the inside post soldering. So I was wondering if there's any way to prevent the stains and whatnot that form from heating up the metal while soldering

 

[farmer57]

Sounds like you are working with roughly 24gauge metal, which can only be so hard due to it's thickness. If you impart physical contact to any metal at that gauge - what do you expect? Go with steel if you want strong/durable at that thickness.
Either gold/silver or copper or any of it's common alloys will only be so strong. 18K gold will only be so much stronger, a bit due to extra copper or zinc or other alloys. Not sure what you are making but why not increase to say 18 or 16 gauge?
16 gauge of most of the above mentioned metals/alloys is quite resilient. Tumbling with fine shot can increase the surface strength (so called work hardening) slightly but so does quenching (dropping hot metal into water or oil). If you are going to solder it (I presume it will be hard soldered - not soft) - you can sort of achieve strengthening by dropping it while still hot (especially if you are to use HARD silver solder - instead of medium or easy) into cold pickle - it will achieve dual purpose by cleaning your flux and joints and quenching at the same time. Make sure you hear a very positive 'whoosh' when it enters.
Keeping things on the other side clean while soldering can be achieved. Use charcoal block or similar to reduce oxygen to the piece. There are fluxes and other substances you can use to coat with as well (firescoff, amacote, scalex or such) to contain fire-scale on the other side. Remember that pure silver (fine) and gold (24K) will leave no fire-scale but pretty much anything else (of the commonly available metals and alloys) will.
Good luck!

 

[mdengraver]

Put yellow ocher, graphite, or white out, etc. in areas you don't want solder to flow as stoppage, it can be removed after soldering. When work hardening the metal hit it on the concave side of the dome with a wooden dapping punch into a wooden dapping block, this will work harden to some extent, and eliminate any marring or searching to the metal domes.

 

[purplepepper8]

Sounds like you are working with roughly 24gauge metal, which can only be so hard due to it's thickness. If you impart physical contact to any metal at that gauge - what do you expect? Go with steel if you want strong/durable at that thickness.
Either gold/silver or copper or any of it's common alloys will only be so strong. 18K gold will only be so much stronger, a bit due to extra copper or zinc or other alloys. Not sure what you are making but why not increase to say 18 or 16 gauge?
16 gauge of most of the above mentioned metals/alloys is quite resilient. Tumbling with fine shot can increase the surface strength (so called work hardening) slightly but so does quenching (dropping hot metal into water or oil). If you are going to solder it (I presume it will be hard soldered - not soft) - you can sort of achieve strengthening by dropping it while still hot (especially if you are to use HARD silver solder - instead of medium or easy) into cold pickle - it will achieve dual purpose by cleaning your flux and joints and quenching at the same time. Make sure you hear a very positive 'whoosh' when it enters.
Keeping things on the other side clean while soldering can be achieved. Use charcoal block or similar to reduce oxygen to the piece. There are fluxes and other substances you can use to coat with as well (firescoff, amacote, scalex or such) to contain fire-scale on the other side. Remember that pure silver (fine) and gold (24K) will leave no fire-scale but pretty much anything else (of the commonly available metals and alloys) will.
Good luck!

Thanks for your detailed response. I will try out these things and hopefully will have better results

 

[purplepepper8]

Put yellow ocher, graphite, or white out, etc. in areas you don't want solder to flow as stoppage, it can be removed after soldering. When work hardening the metal hit it on the concave side of the dome with a wooden dapping punch into a wooden dapping block, this will work harden to some extent, and eliminate any marring or searching to the metal domes.

The solder flow isn't an issue as much as firescale. Even with boric acid there is a bit of that and once its there its hard to clean because the areas arent easily reachable.
As far as the work hardening goes- I can't use the dapping block because the back of the piece has a flat sheet soldered on (see video).

 

[mdengraver]

Society of American Silversmiths - Firescale Issues

 

[mdengraver]

 

[mdengraver]

Depletion guilding is one way of overcoming firescale by raising the fine silver to the surface of the sterling silver and eliminating the copper oxides on the surface of the metal through multiple heatings, pickling, and lightly brass brushing with soap and water between firings until a nice frosty layer of fine silver is achieved on the surface of the metal.

 

[rweigel]

When working with silver, try Argentium for your domes. Two advantages:

-it does NOT firestain, comes out of the pickle with a white matte finish after soldering

-your finished piece can be tempered at 300-350 °C 1 hour for hardening without altering the surface (much), it may darken a little bit

attached is a litte piece I made from 2 argentium half spheres recently

 

[purplepepper8]

Depletion guilding is one way of overcoming firescale by raising the fine silver to the surface of the sterling silver and eliminating the copper oxides on the surface of the metal through multiple heatings, pickling, and lightly brass brushing with soap and water between firings until a nice frosty layer of fine silver is achieved on the surface of the metal.

Its strange but I realised that the marks on the metal were not firestain but some small particles kind of 'stuck on the surface. I say 'stuck' because they wouldn't come off in the ultrasonic, but they would if I simply used a brush or toothpick to wipe them off. I was able to prevent firescale

 

[purplepepper8]

When working with silver, try Argentium for your domes. Two advantages:

-it does NOT firestain, comes out of the pickle with a white matte finish after soldering

-your finished piece can be tempered at 300-350 °C 1 hour for hardening without altering the surface (much), it may darken a little bit

attached is a litte piece I made from 2 argentium half spheres recently

Thanks for your reply but as I mentioned silver is just to prototype with the actual piece being made in 18k gold. Does the same tempering method work for gold as well?

 

[farmer57]

Also, don't forget to have your piece very clean to begin with. If you're hard soldering on 'dirty' metal - you might invite all sorts of problems (and that goes for both sides). If I were you, I'd complete all the prep - throw it into warm pickle for quick cleaning (you should be using pickling solutions - sounds like you might be trying to work without it - DON'T) - neutralize it - solder - pickle - neutralize it - tumble if you need to and do your engraving. It really is not that difficult once you get your 'flow' going.
If you really want to get that super fine silver/gold shine back - after all is done - use soft brass brush with thick dish soap solution and give a scrub (dish soap is needed to keep surface from being scratched). This is basically what I do for pre-enamelling prep for transparent enamels application - when cleanliness is pivotal.
Sonic cleaner will not do much for fire-scale.

Good luck.

 

[rweigel]

You could precitipation harden gold as well, but to what extent and how exactly to do it depends on the precise alloy. The supplier of the sheet metal should be able to tell you. I‘m just familiar with some german alloys, it will not work the same way for alloys from other foundries. The general method is to let it cool down slowly from annealing temperature. That‘s why gold alloys are quenched after annealing if you wish to deform them plastically, this way they stay softer.

Cheers

Ralf