cleaning museum silver – sodium carbonate or calcium carbonate?

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    • #131892
      Charlene Martin
      Participant

      Hi everyone 🙂

      I watched the Deborah Long/Care of Metal Objects webinar, and noticed she recommended not using dips, and rubbing the silver with a cotton pad wet with a calcium carbonate/deoinzed water slurry instead.

      A museum professional suggested that I use a Qwicksilver dip kit on my deeply tarnished silver artifacts. It consists of a sodium carbonate/hot deoinzed water dip, which reacts with an included aluminum plate to create an electrolyte reaction to lift off tarnish. I’ve been researching the difference between sodium carbonate and calcium carbonate, and have found that while both are alkaline and metallic carbonates, the sodium carbonate is more electropositive and has a higher PH.

      I don’t have any hollow or concave areas in my silver artifacts – can I dip them in the Qwicksilver solution, or is sodium carbonate too corrosive?

    • #131898
      Marianne Weldon
      Participant

      Calcium Carbonate is inert. If you leave some behind, it might not look good (chalky and white), but it will not react with the surface in a detrimental way.

      The silver dips commercially available are quicker, but often leave tarnish inhibitors such as mercaptans behind. If the actual polish is left behind it can promote corrosion, particularly stress corrosion cracking.

      While it is much more labor intensive, I do believe that using precipitated calcium carbonate (the shape of the precipitated calcium carbonate is less rough and therefore better) is the preferred approach for museum collections.

    • #131897
      Marianne Weldon
      Participant

      I meant to continue with…

      The particular method you referred to I am not familiar with, however, the electrolytic reduction methods I have used before did not leave a surface that was even and clear enough to consider “finished”. In my experience polishing with Calcium Carbonate was still necessary after the electrolytic reduction.

    • #131896
      Jenny Arena
      Member

      Not knowing how to answer this question myself, I went to the source regarding the use of Qwicksilver. Here are thoughts from Deborah Long:

      “Sodium carbonate with an aluminum plate is a very standard method of electro-chemical reduction that has been in use for many years. The problem with these dips/solutions is that they indiscriminately chemically reduce tarnish along with intentionally applied patination, leaving a surface with an odd looking “flat” appearance. Over time, they develop a yellowish appearance that I do not find appealing. Subsequent tarnish/corrosion on surfaces treated this way is also unusual looking. For these and other reasons, I would never suggest the use of this process for museum artifacts.”

      I would always take advice and recommendations with a grain of salt until you’re able to talk to the expert–which thankfully for us Deborah could help weigh in!

    • #131895
      Charlene Martin
      Participant

      Thank you for going the extra mile, Jenny. It’s great to know that some of the experts are happy to help. I always worry about bugging them with silly questions!

    • #131894

      Good Morning! I was very excited to try the recommendation of Deborah Long on a beautiful silver tea set in our collection but couldn’t find the precipitated calcium carbonate available at the recommended outlets. Does anyone have an idea of where to get this? Thanks!

    • #131893
      Anonymous
      Inactive

      Christina,

      I not sure if anyone has replied to you, but I have purchased my Precipitated Calcium Carbonate from Talas. Their website is http://www.talasonline.com

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