Silver Bezel Pitting

Hi,
I’m kinda embarrassed to admit this but recently I have had a heck of a time with pitting along the seam where .999 silver bezel meets a .925 back plate. Both surfaces are sanded to 400 grit and perfectly flat. I use Handy Flux paste and plenty of it!

I use medium wire solder and heat the piece and place wire solder either inside or outside the bezel.

Didn’t have the problem till recently and I cant figure if the metal, solder or flux has changed.

My technique is to heat until it gets clear and the bezel can skate a little on the plate. I touch the solder to the base either inside or outside depending upon the design and where I don’t want to clean the solder from!

I was told to get in and out quick and that’s making it worse suggesting lack of solder is the issue…

The seams look good when filed and then using binding wire use easy solder to solder on a band. I noticed today that the medium solder bleeds out a little during this process and that’s where I suspect the pitting is occurring. I’m super quick with the easy and mostly heat the band (12ga straight 6mm wide sterling) and concentrate the flame at the connection.

It just occurred to me maybe I should NOT clean/file the bezel flush and leave a small lip around the edge and clean up after all soldering complete…
Anyways…please offer some suggestions for this simple Jewelry Making 101 process I am all of a sudden struggling with!

Thanks!

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You might be burning off the zinc in the solder leaving pits behind. Zinc melts at a much lower temperature than the silver and copper in the solder. You probably don’t see this until you finish the joint. Depending on how you finish the joint, you might be pulling out material leaving the pits behind. This happens to me when I use a rubber abrasive wheel that spins in the same direction as the solder joint. I know that I should use a file more than I do, but the wheel is so much faster. You might try a higher melting point solder. I have the same problem from time to time and really haven’t figured out why.

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Interesting!

Ya know what I use blue rubber discs(From Rio; EVE High-Flex Blue Flat-Edge Wheel Polisher, Medium) for near final polish and noticed the longer I “grind” with them the worse it gets! Today I thought maybe I could sand through the pits and they got worse! You may have something there!

I LOVE filing and use a #5 Swiss for final cut, then sand, then the rubber.

I’m pretty quick with the torch and get that glowing tiny meniscus around the edge and stop. I don’t go back over and keep heating. Doesn’t seem to matter…

I used to use hard solder and may go back to that. It’s trickier as the bezel seam is with hard so…

It’s a bummer as it doesn’t show up till it’s all done! I made a nice piece today and tried to grind through the pits with the rubber wheels and it ruined the piece like none other!

Thanks!

I think that Rob is quite right. This discussion is very similar to the problem of pitting when annealing. Zinc is the culprit, as it readily burn off as volatilized oxide when overheated… the other thread about pitting during annealing is addressing a similar problem… try using hard solder with less zinc and a lower temperature flame. I’ve done most of my work with a cheap hand held hardware store propane torch…the flame is not as hot as any gas with oxygen, but sufficiently hot enough to melt silver but not copper very well but still plenty hot enough to solder… it takes prolonged heating to completely melt silver for a pour… I’ve also used oxyacetylene and it’s too hot without turning down the flow of oxygen to get a neutral to slightly reducing flame, and it’s still too hot to use without a lot of caution. Once the solder flashes, stop the heat…if the joint is flush, you won’t need to heat it further to get the solder to completely fill. Oxyacetylene is great for melting a pour, since it superheats the melt, making for a good pour…almost too hot for soldering, especially for lower temperature soft solders.

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I forgot to mention, and if it already has been, I apologize, but you can make or buy a flex shaft mounted tool that will peen over the metal around a pit. They are a type of rotary burnisher. I have made them out of old worn flex shaft tools, but you can also buy them…Rob

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Thanks! I bought a margin roller; the 10mm rounds with 7 steel wheels. Does the trick very well! I tried making one with less success.

BTW I started using hard solder and actually leaving the flame on the piece a second longer. Getting the glowing molten solder to go all the way around at once and keeping a large flame to do.

Thought I’d chime in with a solved problem!

The above suggestions are key, clean flat, perfect fit imperative but even then soldering technique will make it all for naught!

The bulk of my bezels are dime to quarter size and half dollar on occasion. I found the most important thing is to have the solder ALL glowing and molten at once, no cold spots. It seems if you chase the solder around when you get to the other side with solid solder THAT will be an area of pitting! Obvioulsy large pieces more challenging. Use hard solder as well and not sur eif mentioned above but NEVER start your soldering at the solder joint of a bezel, even if bezel is connected with hard and you use easy. The eutectic of the tow solders WILL open that seam! So set your bezel 180° from seam and work over to it and lock it in THEN melt that entire solder joint so its one solid glowing ring! I rarely get piting any more unless I break a rule!

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solved your own problem, experience, congrants.

Hi,

some thoughts…correct me if i am wrong…i believe the pitting occurs as a result of overheating…the zinc in the solder reaching boiling point and vaporizing…

zinc melting point -788F
zinc boiling point- 1665F

silver solder melting points are around 1325F-1450F

copper in the alloy reduces the melting temp of the individual elements

zinc in the alloy improves flow

julie