Experiments with aluminium bronze

Today I made some aluminium bronze, and it was a partial success I think.

I learnt a few things about the material, but I'm sure there's more to learn.

The first thing that I learnt is that it takes a surprisingly long time to melt copper; I was still trying after 20 minutes at full blast. Its melting point is 1084.62 degrees celsius, but either I couldn't get that hot, or there's some trick to melting copper. I got it to a very bright red-heat, but it wouldn't go any further.

So here's the lesson in that: according to The Complete Handbook of Sand Casting by C.W. Ammen, you should melt the copper first (p189), then add the other metals. I got fed up with w

aiting for the copper to melt, so I added my aluminium, which began to melt almost instantly, forming a puddle in the bottom of the crucible. Once this puddle had formed, the copper began to melt really quickly. If anyone can explain this, please do. Anyway, in future, I'll put copper in the bottom, aluminium on top, then more copper, then fire it up.

The second thing I learnt is that either aluminiun bronze is not nearly as golden as the internet would have me believe, or that it's a lot harder to get the ratios right than I thought. I aimed for 10% aluminium by weight, so I put 9 parts copper and 1 part aluminium in (2kg copper, 222g aluminium). One thing that leads me to believe that the ratio is hard to get right is that there was an awful lot of dross (or something that looked like dross) stuck in the bottom of the crucible after the pour. Thus, much of either or both metal oxidized. At what ratio, I can't say, but surely it is likely to skew my intended ratio.

In all honesty, I don't care about the colour, and the colour came out being pretty nice anyway. It looks almost like steel, only shinier. What I care about is the mechanical properties.

Here's an idea of the colour: the watch is stainless steel, the light has made everything a little yellower, though there are some patches about the place on other ingots that actually are that yellow. Also, notice how smooth the side is, and the two big flat bits on the top. The bumpy bits were loose bits of sand. This implies that I can get a pretty good finish with this alloy even with reasonably coarse sand.

The third thing I learnt is that aluminium bronze needs to cool slowly, otherwise it becomes very brittle. I quenched most of the ingots that I cast, with the result that I could break them by hand, or by dropping them from a height of about a metre. This had me worried, until I found an ingot I had forgotten to quench. I couldn't break it at all, I didn't try with a hammer though. In future, NO QUENCHING.

Here is a n ingot that I quenched, it was so brittle that I could snap it in my hand. It leaves a very sharp edge, I discovered the hard way. Notice how shiny the inside is? Also, you can see how it's quite crystalline. This has to be the result of the quenching, as the alloy ratio is almost certainly similar to the range of 'real' aluminium bronze, and I have one ingot, which wasn't quenched, which isn't brittle.

Experimenting with etch resists

Today I tried two substances as etch resists for electrolytic etching. Etch resist marker, designed for chemical etching of circuit boards, and black acrylic paint. Neither were great, I must say. The etch resist pen worked, but came off very easily when I brushed the surface to remove copper crud. It could work, but I'm not doing any fine art with it. The second, acrylic paint, was a TOTAL FAILURE. Tip: Never use water-based substances as resists. They dissolve in the bath. Photo one is before etching, photo two is after.








I didn't touch the front surface on the second one before taking the photograph. Once I scraped the paint off, I noticed that the whole surface had been etched the same amount. I reiterate: Never use water based substances. Ever.

Card box pt. 2

I have decided that I hate press 'n' peel blue. It will not work for me. I'm probably doing something wrong, but it took me three goes to get nowhere with it, after that I went back to good ole magazine pages and, lo and behold, perfect first go. Tip for young players, don't buy p'n'p blue. Anyway, I etched the front of my card box today, much better than the old card box I must say. Here's the image:

My card box

If there are two types of games that I love (which there are), they would have to be billiards and cards. Last year I made this sweet, if rather chunky, card box of copper. It had a handmade hinge, and I etched a a picture of the mad hatter's tea party into the front of it. It held the cards well, was sturdy, and the bottom never fell out, not like the cardboard boxes that cards normally come in. Anyway, recently I lent it to a friend who wished to continue playing cards in their free period, something I often do, and the next thing I knew, it was gone. I had the cards, but no box. I don't know who lost it, and I don't really care anyway. It gave me the kick that I had been needing to make a newer, better one. So here it is. It's not done yet, but I've made the two parts of the box and done the hinge. Next up is to put an etching on the front. I expect I will do the same picture as before, but I'll do it better this time, the last one was a bit shallow. But I'll also etch a 500 scoring table on the inside of the lid. Unfortunately, I didn't take any photos of the old one, but I do have photos of the new one.









Here are some of the details. The top is unadorned at the moment, but the bottom has a gear from an old broken German cuckoo clock that I found soldered on to it. I made the hinges with some very small copper pipe, I cut it to the length of the (short end of the) lid, plus a little extra, then cut it into thirds. I cleaned the ends up, then put some flux on the pipes and the edges of bot the box and the lid, pushed them into position lying on a tile, and gently heated them, then added a very small amount of solder.









The pin running through the pipes is some brass wire.








The old hinges were made from copper sheet, folded into a rough tube at one end, then soldered onto the rest of the box. Funtional, but chunky and fiddly. These ones, while fiddly, were actually easier than the old ones, and are almost invisible.

A plan for the future

I was talking with a friend of mine recently, and discovered that her father is a lithographer, and, as such, does copper etchings. She said that he did acid etches, which piqued my interest, so I have done a little research, and come up with this. It's called the 'Edinburgh Etch', and uses Ferric Chloride as the 'acid'. I say 'acid' because it is actually a salt, not an acid. Anyway, I shudder to say it, but...Dick Smith...sell bottles of Ferric Chloride, so I shall purchase some, and start tinkering.

On a different note, a package came from A&E Metal today, containing a sheet of 1mm brass, and a sheet of 0.5mm nickel silver (which actually contains no silver), and some brooch backs. I intend to try and electroplate the nickel silver onto brass and copper. But we shall see.

An experiment in separation

I have found that when I etch, the plate that I'm etching heats up to a point where the toner flakes off the plate, leaving the copper underneath exposed. This evening, I decided to try and change this. in the past, I have put the two plates very close to each other, about a centimetre apart. While this positioning means that it only takes about twenty minutes to etch a plate, I think it contributes to the heat.

Anyway, I transferred this picture onto a piece of copper, and put it into the etching tank. The picture was from the front cover of the first issue of this magazine.
But this time, instead of putting the two plate really close together, I put them on opposite sides of the tank. Because the resistance would be much higher, I knew I would have to leave it for a lot longer than normal. I put it on at 15 volts, and between 1 and 1.25 amps, and came back 50 minutes later to check it and turn it off, as I was leaving the house to ferry lurkers around town.

When I got home again, I turned it back on again, and got to tinkering around the workshop. Another 50 odd minutes later, I turned it off, this time for good. Not as much toner had fallen off as in previous attempts. Success! I got a nice gradation of depths, deeper in the wider lines, shallower in the narrower. Then I cleaned it off, and inked it. Here's what it looks like.

One thing that I have noticed with using magazine pages for toner transfer, is that parts of the image from the magazine sometimes transfer too.You can see this above and to the left of the bird. So sometimes, my etchings end up with words etched into the background and other things like that. At some point, I will attempt a different paper.