Sunday, January 12, 2014
Copper Mug Set
A pair of hand raised copper mugs. This was a commissioned set for a Christmas present.
Process pics after the jump.
A guy I ran track with in high school found some of my work online and has been commissioning work from me every Christmas for gifts for family members. I couldn't be more happy than to do this kind of work. This year he was looking for a set of "beer drinking" copper mugs. We agreed on a pair of raised mugs that would hold at least 12 oz. I'd done a smaller mug before just for practice, so I was confident that I could do it and I was pretty sure what size material to start with. Because they were to be raised from a single flat sheet, not seemed and soldered from multiple pieces, I had to take into account the size of the base, the height of the walls, and also how much the copper with stretch and deform as it is hammered. I decided 8" disks of 20 gauge would do the trick. I also wanted to do an extra one as a kind of prototype so I could try various techniques on it before I did them to the other two.
I purchased a 12" x 24" of 20ga. copper and started cutting out what I need. First was the three 8" squares which I cut with a pneumatic jump sheer, then I scribed a circle on each one with a compass and cut that out by hand with aviation snips. A little cleanup with a file to take off the burrs and I have 3 nice round circles.
The center is permanently marked with a center punch, this provides a reference point for the rest of the process, and I laid out the size of the base, along with lines to show where I would put my crimps. Crimps raising is a good way to start something this size, especially since I want the walls to come all the way up past vertical eventually.
Here's one of the pieces on my crimping stake, which has a narrow valley that tapers to the point. I hammer from the top with a plastic mallet with a flat narrow head.
All three crimped disks.
I then will flip the piece over and work it over the same stake to deepen the crimps even more, which will help bring the sides of the mug up a little bit further before I start the raise them up.
The crimp folds then get hammered out over my raising stake with a metal hammer with a narrow face. The peaks of the folds require a good deal of force to flatten out, and care must be taken so the metal doesn't fold over on itself and form a crease.
After this is the standard raising process, working from the edge of the base up to the lip of the mug in concentric circles, annealing between each course and resetting the base on a bottoming stake so it remains flat. A more detail explanation of this set can be found on some of my other posts, no need to rehash here.
After 3 full courses the mugs are at this stage. Because I want them to have a somewhat rounded globular shape, I'll start the next course of raising about an inch up from the base, which will help maintain that very bottom angle.
Another two courses brings the top section of wall up to vertical. I should mention that I have been raising all three mug simultaneously with the hopes that it will keep them as identical as possible.
The last course was started an inch or two below the lip, and brought the walls in past vertical and started to really constrict the lip of the mug. I was happy with this as the final rough shape. I then rounded out all the corners from the angle raising with a mallet, and got the pieces annealed and pickled for the final planishing operation.
Here's all three mugs with one course of planishing, which is where I'll leave the surface for a rough textured look. I then trimmed the top to a smooth regular lip, and rolled the edge over the to give it strength and a better mouth feel.
At this point I took my one extra mug and decided I wanted to try and tin the inside. The tin acts as a barrier between the copper and whatever liquid might be in the mug. Copper is reactive to certain liquids, namely acids, and should be used with a liner to prevent the formation of copper salts in the liquid, which can be poisonous in a large quantity. For the majority of uses copper is perfectly safe, (your water in your house probably flows through copper pipes) but I wanted to try this technique basically just to see if I could do it. I had limited success with the process. I was able to get the majority of the inside coated with a somewhat even layer of tin, but then I ended up burning off a bunch of it trying to go back and re-tin a couple of light spots. I need more practice to be able to control the heat of the piece and a better understanding of how and when to apply the flux. I used the traditional tinning flux sal ammoniac (ammonium chloride), which gave out thick clouds of white smoke and largely obscured my view of what was going on inside the mug. Just another thing to practice before I would confidently offer it as a option to a customer.
Here are the final two mugs. They have a rolled top edge and a handle riveted on. I gave the outside a light patina with liver of sulfur to emphasize the hammered texture, but the inside is left as raw brightly scrubbed copper. They hold about 16oz of liquid, a sizable amount for a raised copper vessel. All in all a very enjoyable project, one that I wouldn't mind making more of in the future.
Thanks for reading and please email me at firstname.lastname@example.org with any requests or inquiries.