Tag Archives: Calking

Raised silver bowl, calking for a thickened edge

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Wato wato all, back to the making of the Britannia silver bowl.

I feel somewhat of a fraud, talking about the thickened edge here as the completed bowl was not a complete success, having not gone entirely to plan. Annealing is a topic I will cover in another post, suffice to say at this stage over, or under annealing causes problems. In this case, near the end of raising the rim cracked. This meant I had to cut off my, hard fought for and carefully made thickened edge. Oh well, at least it wasn’t a complete disaster, I am still happy with the end result. I will explain in detail later in this process.

Quick re cap, the peening process moved material from the centre of the disc towards the edge. Calking pushes the edge down compressing the edge in on itself thickening the edge in the process.

Just as the raising process work hardens and will crack the silver if overworked, so only a single overlapping blow is desirable, or wise, at each and every calking stage for the same reason.

With the bowl to be resting on a sandbag for support, a soft faced cross peen hammer, I used a modified raising hammer, is bought down confidently, striking the edge. Accuracy is very important, each blow ideally overlaps slightly to lead into the next blow. The hammer must be square on, if not sharp ding or undulations will develop leading to uneven distribution of the silver. This will cause problems further down the raising process as the sides will become uneven, worse, it may encourage cracking due to the added stress caused by the gathering of a forceful blow on a very small ‘ding’. It may not develop into a crack until further along, you may not even be able to find a cause when it happens.

A thing I have learnt working with this slow process is that, you may well be able to cover up a misplaced blow, even forget you made it, the silver wont!!!!

Sooner or later something will happen, I will show uneven raising examples another time. The message I wish to convey this time is, take your time, don’t just hit it, measure and control your hammerblows. If you don’t, and hit it willy nilly, it will come back to haunt you later.

I found, as Christopher Lawerence showed on his demonstration, I had much more control and more feeling by holding the sandbag on my lap the whole time. Same rules as raising, move the disc, not the hammer, concentrating on keeping the hammer blows consistent and square to the edge. The picture shows one of my raising hammers that I softened, rounded off to reduce the chance of catching the edge of the silver with a sharp edge, as seen on the opposite side of the hammer showing the original as it came factory finished.

Knocking off removes the burr that is created by calking process. The beauty of this is that material is saved by re compressing it back into the rim rather than, as you would be forgiven for naturally doing, removing the burr with a scraper or file.

As can be imagined this is a delicate process, too hard and you will remove all of the work hammering the rim back on itself, too little force and the burr remains causing problems further along. This is done on a flat plate, hammering from the inside on a steel flat plate in the early stages. Later it becomes impossible to get a hammer in as the opening reduces in size. The picture of the copper one shows the knocking off process done on a mandrell. The hammer used is a collet, of domed faced planishing hammer.

Remember the pickling process is your friend. Every time you strike the silver it will stand out as a shining mark that clearly stands out from the pickled matt finish. No excuse for overworking as you can see where you have been, again don’t just hit it, measure your blows and make sure you are as consistent as possible.

After each round of sinking, then raising, calking process is applied until the end of the raising process, or when the desired thickness is reached, whichever comes first.

Hope you can follow this, please let me know if I’m not clear on something and I will add to this.

Thats all for now, raising proper starts next time, untill then. All my very best wishes.

Stu Art./

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Silver bowl project; peening to make ready for thickened edge

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I watched a film made by the Goldsmiths company to showcase silversmithing skills. The demonstrator was the awe inspiring Christopher Lawrence;

http://www.pearsonsilvercollection.com/biographies.html#lawrence

Christopher Lawrence embodies, for me anyhow, what is it is to be a true master craftsman. If you stop to dwell too long on his achievements, experience and sheer depth of knowledge, you could be forgiven for being disheartened. Trained from a very early age in a time when measurable performance meant far more than ideas and promise, it feel its fair to say the likes of these crafts masters are becoming ever rarer in a time where talking is far more valued than ‘walking’

Rant over! Lets look at peening the disc of Britannia silver before sinking, in preparation to raising. Peening is the same as the approach I presented in a previous post showing how to make simple curves or dishes without curved stakes. The difference being the working from the centre, as before, this time without the ‘dam’ or ‘moat’ I explained to contain the ‘wave’ of material as it is pushed to the outside edge.

The hammer I used is another junk shop find, very heavy, re-profiled and polished to act as a peening hammer. Consistency, as with much of this discipline, is key. My thinking was that a very heavy hammer can be used to keep the blows consistant. Rather than swinging a lighter hammer, with all the variance this would introduce to the force of each blow, I use the weight of the hammer. You see the gentle curve of the hammer face, all blows overlap to keep the ‘wave’ ahead of, and not behind the next blow. Working from the centre to the outside edge, a section of material at the edge is left. All the material is now concentrated there and ready for calking, more on that in another post.

I lift the hammer as precise a distance from the disk and let it fall on the disc of silver. My reasoning being if the height is consistent, the weight of the hammer will ensure the blows are as consistent as possible, I just have to ensure I keep turning the disc to present the next point of contact for each blow. Do not move the hammer, just the disc of silver flat on the steel trist, working in a perfect circle, hence the guide lines made with a compass, moving outward towards the edge.

The little copper model shown here with the calliper showing the width of the rime is to illustrate the sort of expansion you can achieve. The starting sheet of copper was 0.9mm thick. As you see from the digital read out, the size difference is substantial.

I followed Christopher’s lead and did three rounds of peening to achieve this result. Next time I will show you the stages that follow on from this to create the thickened edge as you go along raising your form.

Untill next time, all my very best wishes.

Stu Art.