Saturday, January 8, 2011

Rande Bly compares the makeup of Sinclaire mirror black to Steuben.

The other day the subject of separating Steuben Black and Sinclaire’s black came up. I mentioned that I might be able to help with that. I have information that may help with this subject if it proves true. It was Sinclaire’s brother who talked him into trying black glass for a gift he wanted to give. He told him he thought the color could be achieved by adding more cobalt to their cobalt blue, Sinclaire gave it a try and it worked. Steuben’s black when held to the sun is the color of potassium permanganate, This is shades of Magenta. I was told this by Erickson about 40 years ago and it is correct.

Sinclaire’s black, as the story goes, was made from cobalt. It should show only cobalt blue when held to the sun.

This is a very easy back yard test and should prove to be 100% conclusive. Carder preferred his Mirror Black because it was a softer black glass and easier for cutting. Cobalt colored black glass is extremely hard to cut or etch. Steuben Mirror Black should also have a shinier surface.

Those of you that have a piece of Steuben Mirror Black can see it’s unusual black interior color by taking it outside and holding it to the sun .Find the thinnest area in the glass you can. The ball of the sun will be potassium permanganate in color. An Ivory piece with a black foot will be the easiest to see this with.

If Sinclaire’s black does show only cobalt in color we would have a way to easily tell the difference that could be used as a standard from here on out. I have seen only 3 colors of black. They are cobalt blue, potassium permanganate, and dark green.

I will include a picture of the color of liquid soluble potassium permanganate. The picture is good because it shows the different shades of color depending on different thicknesses of the solution. Steuben’s Mirror Black will show all, or some of these shades of Magenta also dependent on thickness. If the Steuben Black is very thick you may see only the reddish purple dot of the sun.

I am certain if the story is true as written in the book H. P. Sinclaire Jr. Glassmaker by Estelle Sinclaire Farrrar on page 34 that his black should be cobalt blue in color. In very thick pieces you should see a cobalt blue dot of the sun. The story tells that Sinclaire got his black by adding more cobalt to their cobalt blue.

Wouldn’t it be nice to never confuse Steuben Black and Sinclaire Black ever again and be able to tell the difference immediately?

If someone from the club has a piece of Sinclaire black and a piece of Steuben Mirror Black could they check this? If Sinclaire’s black has the internal color of cobalt blue(the most common internal color of black glass) we could use this conclusive information in the future when attempting to separate Steuben and Sinclair Black. I think this would be invaluable if we can show that this is true or not. It should be very easy to find out.

Rande Bly

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