The discussion about testing several anti fire scale fluxed has led
me to make several comments.
First I must admit that I manufacture Cupronil. Because of that I
normally do not comment about Cupronil as I do not feel the orchid
section for comments from members is a place to advertise.
a little history: Early on in the development of Cupronil I learned
that comparing the anti fire scale capabilities of fluxes is very
My partner, a chemist who worked in a crime lab, and I were given
the formula for Cupronil by a noted Hopi Silversmith Laurence Saufki.
He gave me a sample of his flux with the comment it prevented fire
scale when soldering. Being cursed with fire scale when soldering I
said RIGHT!!!. But it did exactly what he said it would. It
prevented fire scale.
My partner felt he could improve on the formula so he would concoct
several batches and give them to me in bottles marked A, B, C etc.
It was my job to test each batch and decide which worked best. That’s
when I learned that it is difficult in comparing the fluxes.
In the early days Cupronil was applied to hot silver with a soft
brush. That in it self took a lot of patience. Too cold and the flux
would puddle. To hot and the brush would stick to the silver.
After MANY trial I was presented with the final three bottles of my
partners concoctions. The one I selected was the exact formula
Laurence gave us.
I learned several things while testing my partners concoctions. If
the coating is too heavy the affect can sometimes be less affective.
I learned that some sheet silver came with a coating of fire scale.
You can imagine how I felt when I tested anti fire scale flux on this
silver. All of a sudden nothing worked.
I learned that Cupronil is not as good of a flux as Handy Flux at
the solder joint. I use just a dab of Handy Flux at the solder joint.
To much Handy Flux will flow from the joint and wash away the anti
fire scale coating producing a terrible ring of fire scale around the
I learned through testing that the various anti fire scale fluxes on
the market all work to varying degrees. I may be prejudice but I feel
Cupronil is still the best anti fire scale flux on the market.
However I think that what ever anti fire scale flux works best for
you is the best anti fire scale flux for you.
There is absolutely no reason for anyone soldering sterling silver
to get fire scale.
Lastly I will say I am very proud of our product as it has prevent
fire scale for many silversmith for at least 34 years.