Dundas: Galena to Flake White

This article is a series of journal entries from the 100 mile ART project, a project completed while artist-in-residence for the City of Cambridge in 2008. The goal of the project was to create a painting using only materials found or farmed within a 100-mile radius of Cambridge, Ont.

Galena

The last sample provided by Reiner Mielke from the Dundas quarry was of the mineral galena. Galena is a natural form of metallic lead sulfide, and herein lies my quandary … lead. Is there any proper use for it?

Over the centuries it has ended up in some pretty questionable places. A history of lead could begin with that fact it was used to sweeten Roman wine and end with it being used as an additive to automobile fuel. Both of these uses are frankly hard for me to imagine and inappropriate because of their broad side-effects.

But, as I’ve thought about whether or not to use this sample, I’ve begun to realize that lead might legitimately have a different history as a pigment. I’ve used it before as a pigment, and I can attest to it being superior to modern whites in it’s properties, but historically it wasn’t just a better white, it was the only white.

I think that it is this historic identity that has especially interested me. Every major art-work in the West of the last two millennia has used this pigment. This can only be said about lead-white! The reds, yellows, blues, greens, and even the blacks, all differed, but the white is common. To me this is really amazing and worth participating in, at least a little bit.

So, in the end, I have decided to experiment with the galena from the Dundas quarry, but in order to be responsible in this decision I propose the two following guidelines: First, I will only be processing the amount of pigment needed to complete the project’s icon (which will probably end up being roughly a thimble-full). Secondly, my children will not be helping in this part of the project.

I guess this entire journal entry could be dubbed as a disclaimer, but this project is intended to be transparent so I wanted to present my thoughts and decision. Of course, if you have something to add, please place a comment on the article.

Separating the Galena

The galena collected at the LaFarge Quarry in Dundas was very pure but it also came mixed with other minerals. This posed a problem, because if I wanted to easily smelt the galena, it would be important that my sample be fairly pure.

After researching some different methods that are used in modern industry I made a few attempt to separate the desired galena using different processes. First, I crushed some samples into powder, impurities and all. Then I proceeded with a special heating regiment, additives like pine oil, and aerated water baths but none of these were successful trying to get the galena to be distinct from the other contaminating minerals. And, in the end, all these experiment left me with nothing more than a new appreciation of just how refined our modern methods are …

After all that I figured out the probably best way to get my nice, pure sample was going to be simply cleaving the other minerals away using an old chisel. I realized that since I’m not looking for an industrial amount of galena such a basic method is quite workable. And, after a few hours of work, I now have a very pure pile (about the size of a flat golf-ball) that I can move forward in experimenting with.

Smelting Attempt

Smelting a rock is something new to me. While I have crushed and then refined many different minerals, and made colourful pigments from them, this process is something I’m unfamiliar with.

Without me writing too much about it, you can probably guess from the photograph above my first attempt at smelting ore didn’t go according to plan.  After putting some pure, crushed galena into a porcelain bowl I placed it over my Bunsen burner.  I’ve been reading about this process in preparation and I knew it was important that oxygen get to the specimen in the beginning (into order to change it from a sulfide into an oxide before trying to melt it) but what I didn’t know was my nice porcelain evaporation bowl wouldn’t take the heat!

But, if you look carefully, you can see that some of the galena has actually started to melt; but only a little bit …

A Little Success

It isn’t much, but using a very pure sample of crushed galena I managed to smelt a little bit of my ore. It has been a learning process for me, here is what I have found out so far: It turns out that it is important to do a two step process in creating this metal. First the powdered galena is roasted (turning it from a sulfide into an oxide). The second step is to reduce the oxide thereby converting it into its metallic form.

Now that I have a small metal sample, my next step is going to be exploring how to best turn it into a pigment …

Smelting for White

In preparation for turning the galena collected at Dundas into flake white I needed some kind of guinea-pig (I wonder if such a phrase is still politically correct ..?) to test my proposed processes for turning such a metal into an oxide pigment.

I don’t know why it came up in conversation, but my neighbour mentioned that they still use lead in balancing tires; and he also happened to have some such wheel weights in a bucket! So outside, and with a good breeze blowing across my little camp stove, I used my little plumber’s torch to melt down these scraps and then cast them into a few aluminum cups.

The work was quick and without incident. Each little medallion released from the cup by giving it a gentle squeeze and I stacked them in a bucket for use in the next step.

My only real concern at present is that I know this sample will not be pure. Wheel weights are roughly 95% lead, but they also have some tin and antimony mixed in them to produces certain properties. These extra elements might have some unexpected impact on my tests (which I will be on the lookout for). Still, it is good to have something other than my little bit of galena to test my theories!

Stack Setup

With all the ingredients prepared, all that remained was to set up. Researching some of the different methods used to prepare flake white was very revealing. I think that I will probably try a couple of different methods, but to begin with I figured I’d start at the beginning.

The “Stack Method” is considered the simplest method for creating lead white pigment and it was also the most common until the 1880’s. Basically it consists of three ingredients being brought together: Lead medallions, vinegar and horse manure (the metal is the base, the vinegar changes the metal into an acetate, and the manurer provides both the heat needed for the process to work and also the carbon dioxide gas which changes the acetate into a carbonate). At least that’s the theory … in fact the Stack Method still isn’t really completely understood and is notorious for less than perfect results with pigment that is pink or yellow, rather than pure white. My favourite science quote about this method described it as being “happy-go-lucky.”  This description alone was reason enough for me to try it!

It made me smile to realise that when I was looking for horse manure I had to choose who I should call. In the end, Henry was good enough to give me a big garbage can full. I’m also using some local apple cider vinegar which is hopefully strong enough. And, in setting up, I had some great helpers too.

At this point everything is set up; I guess we’ll see what happens in a week’s time!

White Crust

I have been eagerly waiting to see what will happen in my attempt to create flake white and I am happy to write that the process of changing my ore into a carbonate is going well. As you can see the little medallions have quickly begun to develop a white crust!

Leave a Comment