# Clean flux/Borax from Silver Bar



## MR.ED (Aug 23, 2010)

Ok question. what is the best way to clean off flux/borax that is stuck onto a homeade silver bar.

Is there a way to use something on the bar to clean and shine it up
thanks guys


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## Barren Realms 007 (Aug 23, 2010)

Try some hot sulfuric for a little bit and it should come off.


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## lazersteve (Aug 23, 2010)

You should dilute the sulfuric down to around 5 to 10% concentration.

Steve


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## metatp (Aug 24, 2010)

I use a little pH down (sodium bisulfate) in some water. I usually heat the water first, but not always.

Regards,
Tom


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## Oz (Aug 24, 2010)

To expand a little bit on what Steve said. The reason for the dilution of your sulfuric is that silver will go into it hot. It is not a big deal or fast, but save this acid separately and reuse it for more of the same. When you are ready to change your “dirty” solution the silver can be cemented on copper.


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## cpt_squish (Oct 7, 2010)

Just found a better way to do this, and its dead easy.

I used Oxalic acid from the hardware store - 10% solution at room temp.

My first silver button was covered with a thick layer of borax glass.

20 minutes in this solution completely removed all the borax - as I understand any stubbon bits will come off by buffing on a cotton buff with a fine finish (really shiny), but I didn't need this

All the other acids will slightly dissolve the silver - and sodium bisulfate has problems with stainless steel and will sometimes plate copper on the article if its not pure ie stirling silver, and most must be heated

Oxalic acid dissolves the least amount of silver (0.05mm/year), and is compatible with stainless and has almost no problems with copper. It doesn't even need to be heated - but can be if you really need that borax off now, 2-3mins at boiling!


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## Fournines (Oct 7, 2010)

Just use a hammer.


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## goldsilverpro (Oct 7, 2010)

Everybody has their own methods to remove slag. Here are some of mine. I rarely needed acids.

For small, smooth Au or Ag bars with a little slag here and there, I have had good success using a clean 3/16" - 1/4" round steel rod about 6"-8" long and just gently tapped the slag (with the side of the rod about an inch from the end) to shatter it. Once shattered, to remove it, put it under running water while rubbing it gently with your finger. This works well and won't damage the surface if you're careful. You can also tap the slag while under running water. If the slag is down in a hole, you need some sort of a small probe to carefully break it up. Rinse it out with running water or use the probe under running water.

If you don't care about the surface, both ends of a welder's chipping hammer work well.

For large bars, an air needle scale remover works fast and complete. Of course, it will somewhat alter the surface appearance.
http://www2.northerntool.com/air-tools/item-15763.htm.

For large silver bars with a thick (say, 1/4" or more) layer of slag, I usually used a small, short sledge. Often, it works best to put the bar on edge and beat along the Ag/slag interface. Sometimes, it works best to just lay it flat and beat on the slag or turn it over and beat on the silver side. Sometimes, the slag will all come off in one piece but, often, it won't. Sometimes, it's really stuck and you have to beat the hell out of it. A chipping hammer will remove small amounts of residue.


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## cpt_squish (Oct 9, 2010)

Chipping is a good way to get most of the large slag off. 
But as I found out borax splinters terribly and can get stuck in fingers with lots of pain and blood, and its very difficult to see to get it out. Rinsing underwater helps but pieces linger on the silver button, so I might suggest gloves

Its good but given how easy oxalic acid is to use and how clean a surface it produces, I will use this method in preference to chipping anytime!

Air needle scaler sounds cool - might be worth a look!


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