VerdiChem and Conservation

The purchase of VerdiChem by a regional collector this week serves as impetus to provide a simple advice column and reflection on its utility in conserving bronze. As always, I refer to previous blogs to remind myself of what I’ve attempted and previously noted:

The above blog post is very much in the realm of intervention and should not be a collector’s go-to for learning; more so a warning. This post will provide a brief update on my understanding of conservation. First, the success story:

Hard to believe that the coin below is actually going to grade AU58, isn’t it? Well, that was indeed the case but it took a number of years before getting to that point. We can see that the coin is one and the same by the dark alloy streak under the N in PENNY.

Pro Tip: From a Canadian Art Conservationist I can confidently suggest cleaning such a penny with warm, soapy water. I use a pig’s hair paintbrush, which I researched and found it to be one of the softest brushes available in art shops. Cut the bristles down to stiffen the brush. Avoid synthetic nylon brushes. An airtight jar (the clampable jam jars are ideal) containing pure acetone (available at auto shops) can be used to soak the coin after washing and rinsing under water. Acetone will soak up any H2O residue on the coin. Give it a couple of hours. DO NOT USE PLASTIC TWEEZERS TO REMOVE A COIN FROM ACETONE. Acetone is highly volatile; careful not to be overwhelmed by the fumes.

Caution Required in Conservation

TEC sells a $10 kit consisting of white gloves, microfibre cloth, ear buds, toothpicks and makeup removal rounds. The following is a list of damage sustained with this kit:

1. Lining up coins for VerdiChem application and starting with dirtier coins, finishing with better grades of coin. A drop of VerdiChem on every second coin is sufficient to the task; note that the makeup round becomes ‘greasier’ as the product accumulates. HOWEVER, transferring too much gunk from the dirty coins risks scratching coins down the line. Start with quick applications of product on better coins and then use that round on the dirtier coins. Throw away once too much gunk (the round will go green) has accumulated.
2. I recommend ear buds of cotton with paper stems. Plastic stemmed ear buds risk scratching the metal if used overzealously. I have not managed to do so to date and suggest collectors avoid the cheapest of product for this reason.
3. Toothpicks are ideal for clearing out blocked letters in the legend and gunk in between the denticles etc. I have scratched several coins, usually by the application of force beyond what was appropriate to the task. Namely, the attempted removal of verdigris that had eaten into the metal. Surface verdigris is possible to remove between the ear bud, the toothpick and the warm water soapy clean. Verdigris that does not move with a bit of pressure is likely embedded in the metal itself. Continued attempts to remove it will risk damaging the surface patina.

The coin below is a good example of compromise. While the surface grime was easily removed, the spot of hard oxidation under the date did not yield to efforts with the toothpick. It was left as is and nonetheless achieved a solid result at MS63.

The Final Do Not Do

The coin below was of such a colour that I generously applied VerdiChem and let it airdry. Bad idea! PCGS have a chemical sniffer and they subsequently detail graded this coin “Lacquer-UNC Detail”. The coin has a beautiful glossy luster not reflected in the image below (PCGS’s sweet spot for imagery was about 5 years ago). That’s what the VERY CLEAN microfibre cloth is for – the removal of residual VerdiChem. It’s intended to block further oxidation at the molecular level and PCGS accepts its use. Just don’t paste it on too thick. Click on the image to see the PCGS certification (opens in a new tab).

Real World Results in Conservation

Below is a real world example of how VerdiChem takes a pleasant UNC dated penny and brings it back to mint lustre. Even with a modest mobile phone shot one can see the dull gloss of the coin’s surface. I always recommend buying better to begin with and subsequent restoration is both easy and profitable. It makes a good coin more attractive. In this buyer’s market, that’s an edge to have. Click on the VerdiChem image at bottom of page to purchase yours. Cheers, Les.