Delft clay casting pt.2: dealing with gas porosity, ring band moulds, and something akin to progress.

I spent another week learning how to cast metal. And today got pretty close to obtaining satisfying results. I'm not quite there yet, but I saw the light at the end of the tunnel, so to speak.
Last week I've ordered 20g of pure silver casting grain, to make more of my 30%silver 70%copper shibuichi alloy. I made about 5g (as I already had 10g of alloy, and I didn't want to melt all of it at once) more, and tried to cast something presentable.

It was a right amount for the wolf model, but I was still getting loads of porosity. Yes, I learned that those bubbles I was getting in the casts are result of gas porosity: apparently, gas can dissolve in molten metal. That was news for me. And using flux is supposed to eliminate it. However, I was using flux, and still getting the bubbles in my pieces.

So I went back to browsing the web, and at some forum (I really don't know where, sorry) read that if there is even a little bit of solder on the metal you melt, it will behave terribly in castings.

That got me thinking. I melted art clay pieces that I just gave up on. I did my best to clean them, but it was possible that some solder made it into the alloy. So I made another 15g from scratch, using only the casting grain and well-cleaned copper. And that actually helped a bit.
See here:

It's so tantalizingly close to good cast, I don't even know if I'm happy or frustrated.

 Sorry about the picture. But you can see that there are almost no pores here: apart from that huge one between the ears, and one on the paw, and, I think, some tiny ones on the snout.
I wouldn't mind the one on the leg that much, actually, but that one smack right between the ears just won't do. Next time I'm casting this piece, I'm going to add a bit more flux and see if that helps. There are more bubbles on the back, but that can be dealt with. But on the front I have very limited options for clean up available. Still, it's progress.

I also have to work on my ring band moulds, as I can't seem to find a good way of making them, and the metal solidifies in the funnel, without filling the mould itself. I, again, searched the net for pictures of how others make their moulds, and found one approach I didn't tried yet. I hope this one will work for me.

Apart from casting, that takes up huge chunks of my time, I also decided to make another cuff, and made project for another one. I could really use guillotine cutter, or good metal shears, because, even though I'm getting comfortable with using my saw, and getting to even like it (and that's a huge surprise for me, let me tell you), I absolutely abhor cutting through such thick sheet. I mean, it takes up to 15min to cut out 15cm x 2.5cm blank for the cuff! And after passing some length mark ( somewhere between 5 and 10cm ), my saw frame gets in the way, and bangs against the sheet, and keeping it going in straight line is tricky.
Anyway, here's how the cuff looks right now:

Unfinished cuff

It's close to finished, but I need to clean the etching up a little bit, and then of course oxidise it. I formed it, and then slapped myself in the forehead very hard, because I need to use gravers somehow on the etching! That means I need to flatten it again. I get overexcited sometimes, adding myself more work. But that's minor issue.

I also almost finished those lockets I've been working on for forever now. I have to clean them up, add all the finishing touches... and figure out what to do about a teeny-tiny slit that appeared in one joint on the raven locket. That's major reason as to why I haven't finished them yet.

So, that's it for now. I hope I'll have finished, nice castings next week!
Till the next time!
Kasia.

Delft clay casting, pt1: tools issues, copper issues, and a lot of issues in general. And shibuichi.

If you're following me on google+, you may know that I recently ordered supplies for casting. I have a lot of scrap copper laying around, and I wouldn't be able to make anything out of it, so I've decided to try my hand at casting. This way I could still use that copper, and it wouldn't be wasted.
 So, I've got my waxes, crucible, tongs, and of course the delft clay, and got to casting. And found out that melting copper is a pain. It either wouldn't melt at all, or wouldn't stay liquid long enough for me to pour it into the mould. It was frustrating, to say the least.

Tools!

I've spent 1.5 day trying to melt the copper. Then, at the second day, I manged to do this, and it aaalmost stayed liquid long enough to pour it, but it hardened as it was flowing toward the edge of the crucible. I deemed that partial success, and was eager to try again, and that's when I noticed this:

 

Poor torch :(

I did manage to melt the copper, but the plastic casing of my torch... not exactly melted, but, well, did what you can see in the pictures. I got pretty scared it wouldn't work, or that I wouldn't be able to change burners, but after it cooled I found out that I can remove the burner and attach another, the torch works, and the only damaged part is the upper right hand side of the casing closest to the nozzle.
Thankfully, the damaged part isn't anything vital for the torch operation, and the damage is superficial, and limited only to this side.

Feels ;(

But it's pretty clear that one won't melt copper without taking damage. So I had buy another. At first I wanted to order something via internet, but then anything I liked was expensive, and I would have to wait another several days before I would be able to continue my casting experiments, so in the end I went shopping, remembering that the shop I got this torch stocked also a bigger one, without any plastic parts near the nozzle.

It's huge and quite scary

This one makes the biggest flame I ever handled, and unfortunately doesn't have automatic ignition. By now, I got the hang of firing it up, but the first time was scaaryy. Sorry for the crappy pictures, by the way.
Huge flame or not, I still had problems melting the copper. I'm not sure what I'm doing wrong, but I can get it to a semi-liquid state, and then... it suddenly cools and solidifies. I don't know if I direct the flame wrong way or what, but that's what happens.
So I got rather discouraged and angry. I also remembered I had a little bit of scrap silver, and decided to see if I can melt that. And if I can pour it into the mould. It went much easier, though I had to try 3 or 4 time before I managed to get it into the mould without the metal solidifying half-way through.
However, I had only 2.8g, not enough to cast anything. But at least I got to practice pouring the metal. It's not that easy.
But I still wanted to melt that scrap copper. And today I read about Japanese copper and silver alloy, called shibuichi. It comes in different ratios: one is basically sterling silver, but there are other kinds with bigger amount of copper. It can be 90%copper 10% silver, or 95%copper 5%silver, or 60%silver 40% copper, and so on. There are also mixes with tiny percentage of gold (like 1%). what's more, it melts in lower temperature than copper and pure silver. I decided to make 70% copper 30%silver mix.
I thought I would have to melt copper entirely before adding silver. But, typically for Murphy's Law, when I needed molten copper, it just wouldn't melt. I got angry, and tossed the silver in when the copper wouldn't get to even the half-liquid state. The silver melted right away. And, surprise, surprise... suddenly I had crucible of fully liquid metal. It took seconds for copper to melt as well once the silver was introduced.
I managed to get it into the mould as well, and quite easily at that.

Crucible with a little bit of metal solidified near the edge. The red stuff is borax. Not sure why it's red.

I don't have enough of that alloy to cast any of the models I have, not even enough for one thin ring band, but I'm going to buy a bit of silver casting grain, and make some more.
It has a lovely colour, kind of silverish-brown with a light pink undertones. It reminds me mostly of pink gold, though it's lighter in colour.
I have only one, bad picture, but here it is:

Partial success at casting

The yellow is patina, it can be easily removed with sand paper. It's not anywhere near perfect, but I'm happy I can melt it, and keep it liquid long enough to obtain the cast. I'm not sure why there are those tiny dimples in the casting. I'm going to rummage through the internets and try to find out.
Ufff... so that was the first week of delft casting experiments. I'm definitely more encourage to keep learning this now that I actually have metal that I can melt. The details wouldn't be bad if it wasn't for those bubbles, holes, or whatever these are.
I hope the next week will be more better!
Till the next time,
Kasia.
Follow my blog with Bloglovin