I am raising this year in college. I have completed a number of lap
seams at this time however I always have issues with them. Sometimes
I need to solder again. Ok often I need to solder again, especially
if I am raising on the piece. Sometimes I seem to have a bubble
inside the seam that shows up after annealing partway through the
process. This is frustrating and the teacher just tells me that I
didn’t do it properly but not what I actually did wrong or how to fix
it other than solder again. So I am asking for advice. I hope to make
several small lap seamed pieces as practice over break so that when I
start the new semester I can properly do my larger lap seam for my
teapot.
Without seeing exactly what the failure is, and where it is (along
the joint) it’s hard to say exactly what the problem is. If it’s in
the middle of the joint, it’s likely that you got the seams too far
apart when soldering, and ended up with a thick seam. Silver solder,
for all of its wonderful properties, tends to be brittle, especially
when being pounded upon. Make sure the joint ends up the same
thickness as the parent metal, when everything’s done. Make sure the
binding wire is tighter next time. Pay close attention to (A) making
sure the angle of your lap is the same on both sides, and (B) that
they mate well, even in the middle. I sometimes ran stitches up
along the inside margin of the seam, to stop the laps sliding past
each other in the middle. It seemed to help. (It also seemed to force
the noses of the laps down against the other sides if I angled the
stitches a little.)
In school, I tended to use thick sawblades, so I was forever getting
blowouts at the ends, where the tabs were. The solution was to use
thinner blades, so I had a very small kerf between the tabs and the
body. Ideally, offset one set of tabs by a blade’s width, so that
there’s no gap between the tabs and the rest of the lap. (easier
said than done, but it is possible.)
It’s been a long time, but I have a memory of an older book with a
very good discussion of lap seaming. It wasn’t in the book I thought
it was, so I went digging through my library… I suspect there may
be a decent explanation in Codina’s newish book, but I can’t find my
copy to look. I checked Brepohl and McCreight, and there wasn’t much
that’d be of use to you if you’ve already done it once. There’s a
fairly comprehensive treatment in Heikki Seppa’s Form Emphasis for
Metalsmiths (If you’re taking this in school, and don’t already have
a copy, you should.) It’s a little dense, but stay with it. I’ve been
finding gems in it for 20 years.
I keep remembering an old-school B/W illustration that lays it out
very clearly, but I can’t for the life of me find the book. Maybe
Maryon’s Metalwork & Enameling or something of that vintage. (Dover
reprints. It’s worth the $10.)
It's NOT in:
Feingold & Seitz
Alex Austin's new book.
Bernard Cuzner.
-Make sure to keep the metal flat as you bend it, by clamping it to
a table, or using long pieces of wood to “extend” the vise jaws.
-When you bend the “tube”, I find it best to divide the metal into
6ths. Put “soft”, rounded bends 1/6th of the distance from the seam,
and then bend the rest evenly. This puts the seam in the middle of
the straight side of a D. This structure holds together well for
soldering.
-make sure the seam fits well. If you have to anneal before
soldering, be sure to flux and anneal the seam
-I think it is better to use a bit too much solder and clean off any
excess, than it is to have to re-solder.
-When you say that the teacher tells you to solder again, do you
mean that you are told to fix the bubble, or to start over? Because I
think it is pretty common and normal to have to fix little areas of a
seam as you work. Just solder it, and keep working—don’t agonize.
-When you anneal the piece between courses, be sure to flux the seam
to protect it. Also, the flux helps you “read” the temperature.
-When you are hammering, let the seam be in the middle of each row of
hammering. Avoid beginning or ending at the seam—both of which are
more stressful on the seam.
Several items could be affecting your soldering a seam: 1. Are the
areas clean. Not just clean, are they really clean? No finger
grease, no dust, etc. 2. Are you using the right amount of flux? 3.
Is your flame hot enough, are you making the seam hot enough
evenly. 4. Is your solder flowing toward heat correctly? 5. Are you
using the correct temperature and composition solder for your
metal?
Further to #3 above…copper eats heat and if you heat it to long, it
forms heavy oxidation quickly and very easily. So, you must use a
large flame, get in heat it up, flow the solder and get out! If the
piece is large, such as large plates where the heat will be
dissipated, you need a very large heat source.
One more thought: If you are using copper, use black flux, or a mix
of black and white flux. The black flux, made for use with steel, is
better at keeping the copper oxides at bay, and lasts longer at the
sustained high temperatures that we tend to use for a lap seam. And
when you make your teapot, you might want to mix some black flux in,
even if it is silver—under the can’t hurt/might help theory.
Excellent, Thank you so much. Several things I was not doing as well
as it could be. Primarily how I fit it together. Due to the cold snap
and totally unlike Portland snow, I have not been able to get into
the studio but can not wait to implement these ellements. I will also
go buy black flux. Thanks Cynthia. Really apriciate it.