This week's question is one I get asked a lot and involves soldering and enamel. Here's the question from hollymolecule-
I've been enameling for a while but just recently learned some soldering skills- so which comes first, the solder or the enamel? I know there's more than one way to skin this cat, but I'm interested to see what you all have to say.
I'm going to try to tackle this question but realize that this question alone could take an entire enameling course to really do it justice. There are many ways to do this but I'll try to explain mine without writing a book.
First you need to understand different types of solder that are used in enameling.
The first is IT solder- IT stands for Intense Temperature so that is an easy way to remember that it flows at the highest temperature of all the solders.
The second is Eutectic solder- it flows at the second highest temperature and is notable for the fact that it contains NO ZINC. It is composed purely of fine silver and copper. I will explain the significance of this later.
Finally, enamelists also use the regular solders that metalsmiths do- hard, medium, and easy. There is a product called TIX solder which is super low temp solder that I have seen some enamelists use. It can be flowed with very little heat. It is used after all the enameling is done and you need to solder a pin back to the piece, for example. I do not recommend this at all. It is not a strong bond and the color match is pretty bad. This is an example of bad craftsmanship, in my opinion, and is used by enamelists who don't want to bother with real soldering skills. I would never use it but it's out there and I want to make you aware of it. Now, forget I ever mentioned the stuff....
Before we get started with soldering, I would like to post this simple solder chart that shows the temps at which the various solders flow. You will want to keep this in mind when you decide to solder your enameled pieces.
Note that most medium fusing enamels flow at around 1400F- right around the flow temp of hard and medium solder. If you are one of those enamelists who like to fire your enamels hot (around 1500F or higher), you can see that there is no solder that will not re-flow at that temperature. This is important to know- if you have a 3D piece that has been soldered and then enameled, and you fire it too high or just a little too long, the solder will re-flow and the piece will fall apart in the kiln!
So, how do we use all this information? Well, if you are just learning to solder with your enamels I would suggest you start with easy 2D/flat projects. Save the 3D forms for when you become more experienced.
I solder before enameling almost all the time. If I have a complex 3D form that has a high risk of falling apart in the kiln, I would want to use the highest temp solder- IT- and fire the piece lower, especially for the first couple firings. Remember that all firings but the last can be under-fired will no ill effect on the final enamel finish. With each subsequent firing, the solder gets a little "harder". We see this in metalsmithing as well. As the zinc burns out with each heating (either by kiln or by torch), the flow temp of the solder goes up. So, many low firings in the kiln actually will raise the flow temp of the IT solder even higher. This works to your advantage. The only downside to this is that you really should not put enamel over the solder seam so it needs to be used selectively.
Solders that contain zinc (this is all BUT eutectic) will not give good results if you enamel over the solder seam. Zinc acts as a contaminant to enamel and will cause discoloration, pitting, or even pinging off of the enamel. If you need to put enamel over the solder seam, then you must use eutectic. There is no other choice.
If I wanted to do a complex 3D form (or a 2D form) and enamel over the seams, I would use eutectic and be mindful not to overheat the piece in the kiln cause this solder flows at a lower temp than IT. Make sense?
Many enamelists use regular hard solder for 2D pieces that will go in the kiln. This is usually fine and often the solder will re-flow when the enamel flows. They are just too close to the same flow temp for that not to happen. That's OK as long as the solder seam isn't too close to the enamel- you wouldn't want the solder to flow into the enameled area and contaminate it. I would not use hard solder for 3D forms because when it reflows the piece will fall apart.
You can exploit the flow properties of hard solder by also using it AFTER enameling. When you solder with hard, the enamel will reflow and as long as it goes to full maturity, it should look as good as when it came out of the kiln. Just be sure to support it properly because you don't want weird marks on the glass. People who solder after enameling sometimes use enameling trivets and the like to solder on. I personally don't like this approach, but that is just my preference.
Medium and easy solders really don't work well in enamels. They flow too low to hold up in the kiln and if you use them after enameling, they will flow before the enamel goes to maturity. This will leave you with a soldered joint and an underfired enamel. If that's the look you want, then by all means, use this to your advantage. It will be difficult to get a fully matured enamel with these solders.
Remember that you have 2 choices for enameling over silver. One is to use fine silver and the other is to use sterling silver that you have depletion gilded (perhaps another talk for another day). Do not use regular sterling silver that you have not gilded. When you fire enamel over sterling, you will develop fire scale except with the enamel over it, there will be no way to remove it. You will see it forever. Fine silver or gilded sterling will not develop scale like this so the surface stays clean.
As an aside, if you have a way to laser weld silver, by all means, use it. If you do this you will not have to worry about solder at all and you can enamel right over a welded seam. I have a friend who makes these unbelievably complex vessels with enamels and this is how she does it. I couldn't figure out how she had so many solder seams and have them hold up in the kiln-on a vertical vessel, no less. She confessed to me that she bought a welder and there is no solder. Brilliant!
A similar idea is to fuse your metals. While fusing can still fall apart in the kiln, you do not need to worry about putting enamel over a zinc-containing solder seam. This is a wonderful way to eliminate the solder problem all together.
Well, this is just touching on the basics but is a good start. The best teacher is experience and I encourage you to play around with test enamels before you try this on one of your real pieces.
IT and Eutectic solders should be in every enamelists' basic kit- you can get them at most major enamel suppliers.
Now get out there and take your enameling to the next level and have some fun! Til next week, happy metalsmithing.