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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Mon Aug 22, 2016 2:51 pm 
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Hi Ted,
The Delft process is the same as iron casting with a cope and a drag, but in miniature. It's the old story, you can beat your brains out for weeks and get nowhere, then suddenly you crack it and you are away.
The advice about the inert cover gas is good, if you have the kit, otherwise ammonium chloride and wooden skewer is the way forward.
I hope your colon is on the mend?


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Mon Aug 22, 2016 9:28 pm 
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Nope, I just don't seem to be getting any closer :( The result is consistently the same - a one-third to half-filled cast. The metal is really rolling like mercury, perfectly liquid but the instant it touches the clay it solidifies, even with the flame still on it.

It may be that the ring I'm using as a model is too thin. I tried casting a small flat object but the result was the same, worse even.


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Mon Aug 22, 2016 11:01 pm 
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Attachment:
ninety degrees.jpg
ninety degrees.jpg [ 45.03 KiB | Viewed 1147 times ]
This image shows your problem in great detail. Your sprue is at ninety degrees to the direction that the metal needs to flow to fill the ring. The metal is dropping into the mold, freezing at the turn and can go no farther. When metal enters a mold is freezes very rapidly against the mold and the flow occurs closer to the inner part of the flow, somewhat like lava flowing in a lava tube. You need to put the sprue in line with the ring as much as possible. The closer you can get to having the metal go all the way to the far end of the casting without having to make bends, the better. This guy's video is a great example of how to use that particular casting medium:
https://www.youtube.com/watch?v=K0sCDTRwMwg
https://www.youtube.com/watch?v=gtrPX3jEJC4

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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Tue Aug 23, 2016 12:42 am 
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Thanks Michael!

I had wondered if it would work better if the metal could "run downhill" but the way I've been trying to do it is the way shown in the instructional video I received. The aluminium rings don't to lend themselves to having something poured into them like that. I'm not sure how the guy in the video makes it work.

But I didn't know there were so many sandcasting videos either, now I can get some more/alternate ideas.

Cheers


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Thu Aug 25, 2016 10:34 pm 
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Took a deep breath - and carved out an opening with a hacksaw and half-round file in the two aluminium casting rings that were part of the Delftcasting kit so that it looks more like the one in the sandcasting videos Michael posted, except round instead of rectangular. I can now stand the frame upright and pour the metal in through the top, allowing it to flow as close to vertically to the bottom of the mold as the curve of the ring impression will allow. This was impossible the way the frame was, the sprue had to be at almost right angles to the impression and I'm wondering how the guy in the instruction video gets it to work. Just loads of practice maybe?

I was careful not to damage the index marks on the rings so that they can still be aligned. It will require some support since it is round and will roll away if not wedged between something.

I'll give it a shot tonight and see what happens.


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Fri Aug 26, 2016 3:54 pm 
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At the last moment I changed my mind and instead of using the actual ring I've been using as a model, I cut a slice off a length of electrical conduit and sanded it smooth. Pressed it into the modified set of rings. The sprue channel kind of caved in a bit because of the different shape now everything was upright. Poured the silver......successs!!! :D

A fully-formed ring, slightly daggy near the top but a success nonetheless. Put it on my finger with sprue and air hole casts still attached and took it upstairs to show it off. The weight of the thing was just about dragging my arm down and even once all that excess silver is removed, it will still be a very thick band.

I've watched a number of different Delftclay videos now and some of these people are doing exactly what the guy in the instruction video does and what I was doing with the sprue at 90 degrees to the mold...and still getting it to work no problems :?

I'm going to assume my original model was just too thin - though it might work now in the upright position.

Showed wife - she immediately put in her jewellery order :) Going to be a while yet though.

I'm guessing a cabochoned stone will be easier to learn to set in a ring or pendant than a faceted one?


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Fri Aug 26, 2016 4:23 pm 
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Lefty wrote:
I'm guessing a cabochoned stone will be easier to learn to set in a ring or pendant than a faceted one?


Congratulations on the successful casting! Yes, setting a cab is much easier than setting a faceted stone. This is because the often sharp facet junction between the girdle and crown can focus stress onto a very small spot on the stone, causing it to *POP* and spall. Just like making an arrowhead by "flaking". If you're going to be setting faceted stones you can avoid many problems by polishing a slight bevel on that upper girdle edge, (rounding it over with a flex shaft works too, but takes a steady hand). Also, learning how to apply pressure to prongs or bezels helps immensely.

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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Fri Aug 26, 2016 4:48 pm 
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Will the cab still need to sit on some sort of bearing - say a piece of square wire - so the entire flat back of the cab is not touching the bottom?

I've often thought that some of the stones I usually facet could look quite nice as cabs as well. I'm going amethyst digging tomorrow, if I get a nice deep-coloured piece I might cab it for setting.


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Fri Aug 26, 2016 7:19 pm 
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Yes, a cab needs a bearing all the way around. This can be very thin if you're making your own bezels from flat wire or involve the entire bottom of the cab being covered if you're casting your own settings. If you're using a prong setting, it can be converted to a setting for a cab by using the upper rail that holds the prongs together as a bearing, (or you can install a new bearing made from wire).
A lot of traditionally faceted stones look great cabbed. A deeply colored amethyst or garnet makes a great looking cab. In fact if the stone is too dark you can hollow out the back until it's thin enough show better color. This allows you to make a silk purse from a sow's ear, selling lower cost stones at higher prices and looking artsy at the same time. I even remember an article from Lapidary Journal where one of those amazing German cutters had made a large hollow egg from one of those DARK garnets from Idaho. The egg was about 2mm thick all over and had great color in that thickness.

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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Fri Aug 26, 2016 8:40 pm 
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Excellent! Yes, I have access to a private property where I can dig plenty of these, but as you can see they are probably the same over-darkness as the dark Idaho garnets...

Image

Image

They are rather on the dark side for faceting (though I really need to stop dithering and try the designs Gem Ranger kindly did for me)...

Image


But they cab nicely as long as the cab is thin.....

Image

Image

This one would be the ideal subject for the hollow-backed cab you mention (strong backlighting shows it to be quite clean). Barbra actually suggested it to me a while ago but I haven't yet purchased the equipment to do it. I guess I can do it using a flex shaft with a diamond ball burr or something (and a lot of care)?

Image


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Sun Aug 28, 2016 7:41 am 
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Cabochon setting is quite straightforward. Clean and polish your ring (or other piece), then file an area flat to provide a base for the stone. Make the bezel to fit around the stone, make it high enough to curve over the stone (use fine silver to make the bezel, it is softer to work and easier to close over the stone). Solder the bezel in place, polish the inside of the bezel, place the stone in place and burnish the bezel hard against it. Make sure the polish is O.K. and I guarantee your wife will fight you for it!


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Sun Aug 28, 2016 7:47 am 
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michael_e wrote:
Lefty wrote:
I'm guessing a cabochoned stone will be easier to learn to set in a ring or pendant than a faceted one?


Congratulations on the successful casting! Yes, setting a cab is much easier than setting a faceted stone. This is because the often sharp facet junction between the girdle and crown can focus stress onto a very small spot on the stone, causing it to *POP* and spall. Just like making an arrowhead by "flaking". If you're going to be setting faceted stones you can avoid many problems by polishing a slight bevel on that upper girdle edge, (rounding it over with a flex shaft works too, but takes a steady hand). Also, learning how to apply pressure to prongs or bezels helps immensely.

If you wish to learn setting I recommend practicing with silver settings and glass stones. Glass is more fragile than most stones and once you have mastered that you can safely set almost anything.


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Mon Sep 26, 2016 5:06 pm 
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I have a friend who is a manufacturing jeweller (but is a very busy man, hence does not have time to teach me silversmithing) who is moving some of his equipment that he doesn't use all that often nowdays to my workshop. So I will soon have a small centrifuge and burnout kiln at my disposal. This might be an easier way to start learning - I can do more intricate designs than with the Delftclay. Once I've done enough casting and setting of stones, I can start learning how to build things up and solder properly.

Things are progressing (if slowly)..


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Mon Sep 26, 2016 5:23 pm 
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As a tip, learning the skill of lost wax casting is difficult and long winded in itself, and only really of use if you intend to make numerous copies of a model. My advice would be to get a reasonable book on silver and goldsmithing (Rose & Cirino is good, and can be picked up very reasonably from Amazon, Albris or Abe books. Another good point is that it was written nearly 100 years ago so the tools are very basic). Follow the instructions and make some items of jewellery as gifts for your female relatives and very soon their friends will be beating at your door with money in hand!


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 Post subject: Re: Learning To Became Bench Jeweler
PostPosted: Fri Aug 18, 2017 3:52 pm 
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Alan F. wrote:
As a tip, learning the skill of lost wax casting is difficult and long winded in itself, and only really of use if you intend to make numerous copies of a model. My advice would be to get a reasonable book on silver and goldsmithing (Rose & Cirino is good, and can be picked up very reasonably from Amazon, Albris or Abe books. Another good point is that it was written nearly 100 years ago so the tools are very basic). Follow the instructions and make some items of jewellery as gifts for your female relatives and very soon their friends will be beating at your door with money in hand!


Okay Alan, I finally made a start. Bought a couple of pre-cast ring blanks over the past couple of weeks and set faceted stones in them without any breaking or mishaps. They finished up looking a million bucks. Not worth much but both stones have a story, one I cut from the first facetable amethyst crystal I found at the old digging spot (gave that one to my wife), the other I cut from a little smoky crystal I extracted out of a vug in solid granite at a topaz digging site in the far north where a few minutes later, dad fell down the mountainside and was lucky not to be seriously hurt. My son is giving that to his lady friend, he can tell her how his grandfather suffered for it :)

I've managed to accumulate some basic tools - jewellers saw, ring mandrel, various pliers, needle files....even scored a flex shaft in good working order from my sister-in-law's grandmother's collection.

Last night I made a simple silver band from 3mm half round and was fairly happy with how it turned out for a first attempt. Had a couple of goes at soldering as the solder kept flowing the away from the join but I eventually got it to go in the right place. Tidied it up with file and emery, finished off with tripoli and rouge. Beautiful high polish with no scratches visible, only thing was a tiny nick just visible to the naked eye in one side where the solder hadn't completely filled to the edge. Wife decided she liked it and put it on anyway (hooray, I measured and cut the size correctly!).

So I'm on my way, though I have a feeling that making claw settings for faceted stones might take a bit of practice yet.

Question - while I polished the ring blanks before setting the stones, would tripoli round the facet edges if stones were already in place? I can't see it doing much to a sapphire but what about softer things like quartz and feldspar?

Cheers.


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