# Silver Soldering



## dnp101677 (Dec 30, 2010)

I am working on an engine that requires a fair amount of silver soldering. I was wondering if someone could point me in the right direction in the way of supplies. I suppose I'll need everything; although I have a propane torch, but I don't know if I need something special or not. 

It would be nice to be able to find a kit somewhere to get me started. Also, if anyone knows of any websites or posts on this site that explain (on a beginners level) how to do the actual soldering, that would be great too. 

I'm really at a loss here until I can get this stuff figured out. I keep coming up with electronic soldering supplies and directions online, but I think what I need is a little different. I figured for sure someone here could point me in the right direction.

Any help would be much appreciated! Also, I'm in the US.

Thanks,
Dan


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## Deanofid (Dec 30, 2010)

I do a fair amount of silver brazing/hard soldering, and use these guys for most of my supplies:
http://sra-solder.com/section.php/90/1

Get 45% or 56% wire in a rather small diameter. An .031" diameter wire is good for many applications.

A lot of people have trouble with silver brazing because they don't know what flux to buy. Get this:
http://sra-solder.com/product.php/6073/96

There are a number of posts here on silver brazing. Some of them contain some controversy, because silver brazing and proper fluxes are called different things in different countries. You will still be able to glean a lot of info from them. Try searching on "silver brazing", "silver solder", "hard solder", "flux", etc.


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## Ed T (Dec 31, 2010)

For bit of cross pollination you can check out sites about making jewellry. Lost of good stuff. For a bit of inspiration a bit closer to home , check out this site http://modelengines.info/naphtha/Main/ Lots of great pics on soldering up some bits for a VERY nice engine. If the link doesn't work, just GOOGLE "naphtha launch engine". One of the most useful tips (shown in the link above) is the use of small pieces of solder placed at the joint. These are, as I recall, called "pallions" in jewelry-speak and the "so what" is that they allow you to better control the amount of solder you're using and things turn out much tidier than if you feed solder right of the coil. Silver solder is a bugger to get off once you get it where you don't want it. An added benefit is that you don't waste as much solder which, at the price of silver solder, is a consideration. You can do small parts with a propane torch, but it is slow. In balance the chance of turning your small part into a puddle is reduced. Mapp gas is a bit hotter. Oxy something is the trick, but can be a problem with small parts unless you have the right size torch. (see jewellry stuff). Soldering on a fire brick is a big help, especially if your set up is heat limited. As with all soldering, clean parts with good fits, the right flux, the right solder, and enough heat (but not too much) and you can't fail (as eaily). Try it, it's fun and allows some cool parts to be made w/o castings.


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## sunworksco (Dec 31, 2010)

For soldering small parts, I use a MiniFlam torch.
It is the closet thing to laser!
Regards,
Giovanni 

View attachment EZ-PBT.pdf


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## RMS (Dec 31, 2010)

Hi Dan,

One thing I would like to point out when silver soldering parts is to keep all parts to be joined clean of all oil and even finger prints (even if hands are clean)! Then you will need proper flux and filler rod dia. as pointed out, next is a flame that will give the correct amount of heat. If these are small parts that will be less of an issue, but also something to consider. But my point is just make the joint CLEAN!

Rob


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## Jasonb (Jan 1, 2011)

Although a UK supoplier its worth having a read of teh three sections under the lefthand box "Why Braze"

http://www.cupalloys.co.uk/

One note of caution about jewelry sites, they tend to use a higher silver content than us particularly if the work is to be hallmarked. If the solder is listed as Hard, medium, easy or extra easy then its a jewelry solder.

Jason


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## rklopp (Jan 1, 2011)

I made a huge leap in my ability to silver solder successfully when I started surrounding the work being heated with refractory brick. I can easily get away with just a propane torch. I got the brick at a local pottery supply place.


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## Generatorgus (Jan 2, 2011)

I picked up the silver soldering thing quite a few years ago, when I decided to EXPAND my out of control hobbying by making silver jewelry. All of the replies here are golden, good advice. At that time I was lucky enough to find a mini acetyline jewelers torch at a flea market. It is the nuts, as you can vary the size of the flame down to pin head, great for real small stuff and detailed work, as well as a lot of larger things. When I got into model making, some years later, my little torch allowed me to glue bits and pieces to come up with these and quite a few others for a 1/12 scale (doll house standard) working model water wheel mill I decided to build. Lots of fun. Twenty years later, I'm only on my third roll of silver solder, a little goes a long way. Got the last roll off of fleabay, along with the proper flux.






Plain old steel, with some parts made of wood and brass, allmost all of it handwork. Of course, the wood was the most difficult to solder. : No, they don't run, they're just for looking, part of the big picture.
GUS


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## Rustkolector (Jan 2, 2011)

Nice work Gus. If you are going to Cabin Fever in two weeks, you ought to bring these along.

Jeff


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## Mainer (Jan 2, 2011)

Kozo Hiroka (which is spelled incorrectly...) has had some excellent explanations of silver soldering in the course of his various locomotive-building series. If I'm remembering correctly, the instructions for his 3/4"' scale Pennsy Switcher has a particularly good writeup.


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## dnp101677 (Jan 2, 2011)

Thanks for all the great replies! Gus, I too would love to see these at Cabin Fever if you're coming. Nice Work! 

So if I understand correctly. I need to buy the things on the list below

1. Torch - I'm not sure of I should buy a butane or propane. It seems that maybe I will need both and that the size of the work which will be soldered has a lot to do with whether or not one would use propane versus a smaller butane torch.

2. Flux - I think I will use Deanofid's suggestion and get mine here...http://sra-solder.com/product.php/6073/96

3. Flame Brick - I am going to check with a local mason in my area for some of these.

4. Chemicals - I see a lot of references to Sulphuric Acid. Is this all I need? I think I can get this at Lowes, right? Do I just dip my parts in before and after? 

5. Silver Solder - I am still not sure what kind to get. I have some small brass part I am soldering together (.250" diameter). Can someone suggest any specifics of what I need for this? It seems like there is a lot to choose from with the actual solder. 

Is there anything else that I will need to get started? I want to just set up a test station to try and get the hang of it. Thanks again for all the feedback. Your willingness to share your experience saves me a lot of time, I am sure of that!


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## RMS (Jan 2, 2011)

Been a while since I have done silver braze, but I thought this was a good guide:

http://www.silfos.com/htmdocs/product_support/alloy_selection_guide.html

But I would go with what Dean suggested bellow for solder and flux, I think .031 or .025" dia. sounds about right as well as the brands he posted.

Rob


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## Jasonb (Jan 3, 2011)

Beware the Silfos its not the same type of silver brazing allow, fine for refridgeration, Heat & Vent but not really ME particularly boilers.

1. I would stick with propane it ha sa higher calarific value

2. I don't know the US makes but that loks fine, buy solder & flux from teh same suppliers

3. You do not want firebricks that are used in the back of a fireplace you need leightweight bricks which will reflect the heat not absorb & store it. In the UK we use these

4. You want to dilute the acid, citric acid is another option and a bit safer though you will need to pickle for a bit longer

5. The BAg-45% will do, probably 1/32" wire for that size part. The BGa5-45% if you want cadmium free but it does not flow quite as easily

6 small fine brass or steel wirebrush for cleaning parts don't use abrasive papers

J


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## zeeprogrammer (Jan 3, 2011)

Jasonb  said:
			
		

> 3. You do not want firebricks that are used in the back of a fireplace you need leightweight bricks which will reflect the heat not absorb & store it.



Darn it. I just spent $1180 to get 8 split firebricks.
The guy gave me the firebricks. The $1180 was to get him out to repair the fireplace.

Probably fine for the kind of brazing I expect to do. Larger boilers might be a problem.


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## Henk (Jan 3, 2011)

Jason, 

Why the wire brush instead of the paper? 

Henk


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## Jasonb (Jan 3, 2011)

Abrasive papers can caus esurface oxides which restict the flow of teh solder, particularly if you pick up the first dirty old bit that comes to hand.

Have a read of the "Best Brazing practice" in the link I posted earlier it mentions this and also firebricks.

Jason


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## Generatorgus (Jan 3, 2011)

Dan, this is the stuff I bought on Ebay, 50% silver, works great and flows nicely.




I agree with Jason, the alloys in the 45% and 50% range work very well. This one is cad free. The process of soldering is pretty much summed up, clean things well, apply the flux wait for the it to melt into the work before you apply the solder. The snips in the picture are flattened wire and great for small work also a good way to control the amount of solder you apply. They will usually stick to the hot flux, but gravity is good too. The flux is water soluable and can be diluted and applied judiciosly with a small brush, this also helps with over soldering the piece. For larger work I just heat the wire a little and dip in in the flux. If you dilute the flux, it will have a tendency to move your work piece as the water boils out, sometimes cured by gently heating so as to let the steam escape slowly. As for cleaning, I used to pickle all of my jewelry work, but on the models I just give the work a quick shot in the sand blaster. The blast also helps the paint to adhere.
Jeff and Dan, I'll be there Sunday, just lookin around, as I always attend the winter engine show at Jacktown on Saturday, but it would be nice to look you guy's up at the Expo. I've been torn as wether or not to just skip J-town, and show at the Expo, but I have a lot of freinds at the snow show. Lately I've been thinking it would be a lot of fun, maybe next year. I've had the mill set up there once and had a good time, it showed well.
GUS


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## GWRdriver (Jan 3, 2011)

Zee,
All is not lost . . . I have used common residential firebrick (containing clay) as the floor of my brazing hearth for many years. This works well for a base and supports weight and will withstand impact but has little insulating value. The "brick" for insulating value is ceramic product called _light-weight refractory firebrick_. This is a light cream in color (see pic) and is primarily composed of silica. This brick contains no clay and there are various refractory ratings up to 2800F.

Re Jason's recommendation for 1/32" wire to start out . . . No doubt eventually 1/32" wire will be useful for small assemblies but if you plan anything larger I would recomment using a larger wire, 1/16" or larger. It's not a matter of conserving or using less, a joint is going to need what it's going to need, it's a matter of adequate supply to the joint. You will be surprised how quickly 1/32" wire will be consumed and once the joint is up to soldering temperature you cannot be bothered to stop the process while you straighten out another foot of wire.  I think a good plan would be to prepare lots more 1/32 wire than you think will be needed, or have a little of both on hand.


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## Henk (Jan 3, 2011)

Jason, 

Thanks. I still don't fully understand why (if indeed the paper is fresh) but the rest of the writeup seemed good, so I'll just go along. 

Henk


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## shred (Jan 3, 2011)

I'm not an expert but have done this a few times, so hopefully still remember what I had to learn...

 2nd Harry on the regular firebricks being usable. My brazing hearth is made of about seven of them-- two or three on the bottom, two on the sides and back. I do have one of the soft insulating bricks I often use as a platform, but the regular ones can be used for small to medium parts. Someday I'll get more of the soft ones, but I'm in no hurry. Sometimes I've had to make 'caves' of the bricks to get a bigger part up to temp.

I like the 1/32" wire though, since I'm a big fan of cutting rings and lengths of it to lay along joints prior to heating the whole lot.

I did a couple test pieces getting the hang of it, but overall it's pretty simple-- clean everything (workpiece AND solder), don't touch it with bare fingers anymore, flux everything (workpiece AND solder), heat it lightly to dry the flux, then heat the heck out of it with a propane torch, trying really hard not to apply the flame directly to the fluxed area. Heat until you can just about see what you're doing by the light of the workpiece. Seriously-- you'll be at 'cooked carrots orange' before the solder flashes into liquid. Let it cool for a bit (more for steel and materials that don't need to be heat-treated), drop into some water, then into the pickle.

Here's a little video I did a while back:

[ame]http://www.youtube.com/watch?v=WEtUJQuK-z8[/ame]


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## Deanofid (Jan 3, 2011)

Dan, if you are buying a torch, get one for MAPP gas. They look much the same as a regular hand held propane plumbers torch, and will take the same propane canisters, plus they will take MAPP gas canisters. That's what I use for any larger pieces I need to hard solder. It puts out more heat, which you find very handy.

The link I put in my first post takes you to the silver brazing section of that company. Get 45% or 56% silver wire. It will be specification BAg-5 or BAg-7. Doesn't matter what brand, if you buy using those spec numbers, you will get the right stuff.

I like thinner wire because it's easier to wrap around pieces to make a preformed ring. I use mostly .031" wire, and I've been doing this for some time. Harry has made a lot of boilers, so he knows his soldering. We just differ on this thing. I consider the smaller wire easier to use.

For bricks, I've used fireplace bricks for a long time. They work well for me. Stack them up like Shred shows and they will hold the heat around your work piece.

Dean


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## trolley199 (Jan 3, 2011)

Hello from the USA

I bought a PM research vertical boiler kit on ebay - excellent kit - it comes with everything - even the raw materials to make the tools. It came with more than enough silver solder and flux which soldered very well with a common Home depot type propane torch. I am pretty much of a beginner and this was my first boiler.

Lloyd 
New Hampshire


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## mklotz (Jan 3, 2011)

trolley199  said:
			
		

> I bought a PM research vertical boiler kit on ebay - excellent kit - it comes with everything - even the raw materials to make the tools. It came with more than enough silver solder and flux which soldered very well with a common Home depot type propane torch. I am pretty much of a beginner and this was my first boiler.



If it's the vertical boiler, that's not true silver solder. The vertical boiler gets its strength from rivets and the *silver-bearing* solder is just used to caulk the joints.


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## Deanofid (Jan 3, 2011)

As Marv said. The stuff PMR sells is Harris soft solder, 96% tin, 4% silver. Just soft solder with a tiny bit of silver in it. It melts at 430F, which is definitely soft solder territory. True hard solder has to melt above 840F to be considered "hard". That is the definition according to the AWS, who classify such things for the U.S. gubment. Most hard solders melt between 1150F and 1405F, depending on the alloy.


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## sunworksco (Feb 17, 2011)

I'm finding that cadmium silver solder flows better than cad-free solder.
I have used cadmium silver solder for over 20 years now but use lots of ventilation.
Anyone else having the same experience?
Kind Regards,
Giovanni


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## dnp101677 (Mar 22, 2011)

Well, I've been practicing but it seems that I am cannot get the brass hot enough. I am just using a propane torch. Should I be using a differnt kind of gas? I can get the capilary action - the solder won't flow.


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## shred (Mar 22, 2011)

Propane will work so long as you aren't trying to heat up a big chunk of brass or do it outside in the wind or something.


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## picclock (Mar 23, 2011)

Hi

Propane will easily get you to the correct temperature provided you are using refractory bricks to reflect the heat back into the work area. If I remember correctly, propane burns at 1900C, brass melts at 900, and silver solders liquefy at a range of temperatures around 6-800. So if your silver soldering brass your getting quite close to its melting temperature. 







Even with this setup, more bricks on the top make this 'hearth' better for larger items. The size of the item being heated will not affect the final temperature, only the time taken for the item to reach it. The trick is to minimise the heat losses as the final temperature is directly dependent on them (ratio of heat input, heat losses x flame temperature).

I only use a small propane torch but have successfully brazed quite large items, a 5" 10mm thick steel ring is my current record using a small propane torch. (http://www.machinemart.co.uk/shop/product/details/fc109-gas-torch-with-nozzles).

Hope this helps

Best Regards

picclock


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## peatoluser (Mar 23, 2011)

Picclock, I think you've confused the melting points of what i would call brazing rod with the silver solders.
silver solders (silver tin alloy) have a melting point of about 600 - 670 degrees centigrade depending on the grade.
It's brazing rod (basicaly a copper zinc very much like brass) that is in the 850 range.
yours
peter


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## sunworksco (Mar 23, 2011)

You might need oxygen/propane/butane to achieve the higher temps.
I use this with really good results.
I use oxygen/acetylene for large pieces.


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## picclock (Mar 23, 2011)

@peatoluser
your quite correct in that I gave the impression that all silver solders melt at 800C. I get mine from 

http://www.cupalloys.co.uk/popular-silver-solders-leads-to-prices-c26.html

and they list the highest temperature silver solder at 780C, with the lowest at 610C. I think the range of temperatures is so that parts can be soldered in several stages so the first joints don't melt. 

According to Wikipedia, brass melts between 900 - 940C depending on mix. 

I've altered the original post to reflect this.

I really must try to read what I post before I post it ;D

Best Regards

picclock


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## steamer (Mar 23, 2011)

I find Oxy/gas to be too hot.  You need heat for silver brazing.  But you don't want extreme temperature that will burn flux.

A BIG propane torch works best for me.

Dave


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## sunworksco (Mar 24, 2011)

steamer  said:
			
		

> I find Oxy/gas to be too hot. You need heat for silver brazing. But you don't want extreme temperature that will burn flux.
> 
> A BIG propane torch works best for me.
> 
> Dave


Oxy/Propane can be adjusted with the mixing valves for precise heat requirements.
It is infinitely faster than only using Propane.


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## GWRdriver (Mar 24, 2011)

Giovanni,
It's a matter of experience. The reason why model engineers continue to be warned away from the use of oxy/acetyl gear is that in the hands of the typical amatuer, who might only build one boiler in a lifetime, it can be too powerful. It will, as you certainly know, deliver the goods but too much oxygen and an instant of inattention can easily result in a burn-through. Even though I have many boilers under my belt, while soldering a boiler I still need to pay close attention to a few things other than "Am I overheating and about to burn through a sheet?" For the less experienced person this is inviting disaster, hence the recommendations away from Oxy/acetyl. And yes, years ago in a moment of inattention I burned one through and once was enough. I now use both propane and oxy/acetyl, depending upon the specific demands of the job. Also, oxy/acetyl does not burn flux per se, as I occasionally see mentioned, boiling or burning flux is purely the fault of the operator and is the result of applying too much heat too soon, but then again that is much easier to do with oxy than with propane.


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## sunworksco (Mar 24, 2011)

I'm always thinking that everyone is in the hobby for for life.
I use my 3 different torch set-ups for many different uses, including full-scale tubing soldering and brazing.
I just like to have all the tools, just like the tool freak that I am! LOL!
I'm guilty!LOL! I don't mean to be misleading.


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## steamer (Mar 24, 2011)

Hi Giovanni,

As GW said, it's a matter of experience.  GW....I tend to get inpatient...which I have tempered in the last twenty plus years....but I need to keep telling myself to keep the flame away from the joint, but to put it next to the joints....as you know, some setups and assemblies are harder than others to do, and I have used OXY with success, but I've also seen first hand the pitfalls of the inexperienced...and as you said, I try to steer them clear.  I also speak from KOZO's teachings....which I've read several times, where he suggests staying away from OXY as it's too hot.....but...can't argue with success right?

Giovanni...if your successful silvering by rubbing two sticks together...it just means you did it right! ( LOL) ;D

Blaze away!

Dave


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## sunworksco (Mar 25, 2011)

Good Write!
I'm considering using a kiln to solder with paste and solder wire.
I have seen this used and it looks very easy and precise.


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## GWRdriver (Mar 25, 2011)

Giovanni,
There have been a number of times when a small brazing or heat treatment oven would have been just what I needed . . . but my workbenches are full, and my wallet is normally empty.
 ;D


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## sunworksco (Mar 25, 2011)

I know that feeling!
My son and I are planning to join TechShop for learning more about tools.
They have low and hitech machinery.
 I'm very interested in using their 3-D laser scanner and printer.
[ame]http://www.youtube.com/watch?v=V2M9h1cPNBo[/ame]


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## shred (Mar 25, 2011)

giovanni  said:
			
		

> Good Write!
> I'm considering using a kiln to solder with paste and solder wire.
> I have seen this used and it looks very easy and precise.


It's easy, but slow unless you keep the kiln hot.   :-\


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## sunworksco (Mar 26, 2011)

I'm buying this kiln.


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## shred (Mar 26, 2011)

Looks like a nicer version of the one I have. You can do lots of cool stuff with a little kiln like that.


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## Jasonb (Mar 26, 2011)

I though it was for Hot stuff not cool 

J


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## Dan Rowe (Mar 26, 2011)

shred  said:
			
		

> It's easy, but slow unless you keep the kiln hot.   :-\



Have you tried silver solder with a kiln? 

I have a programable controler that I use for wax burn out so I could write a ramp up and down cycle for silver solder, might need some expermentation.

Dan


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## shred (Mar 26, 2011)

Dan Rowe  said:
			
		

> Have you tried silver solder with a kiln?
> 
> I have a programable controler that I use for wax burn out so I could write a ramp up and down cycle for silver solder, might need some expermentation.
> 
> Dan


Yeah, it took a couple tries to get tuned up, but it worked pretty well. I didn't do a lot of it though. If you ramp up with the parts in there from cold you may want to get one of the long-lasting fluxes designed for that sort of thing. Obviously you have to use solder pre-forms or solder pastes since you aren't going to be sticking a rod of solder in the vent port. or anything ;D

Same kiln works well for glass fusing, tempering tool steel & melting small amounts of Aluminum or bronze.


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## sunworksco (Mar 27, 2011)

I have been collecting tools for doing lost-wax casting for jewelry and scale model parts.
I'm also looking at an electric crucible, hot wax injector and vacuum casting machine.
The vacuum casting machine does an excellent job of extracting all of the bubbles out of the molds and castings. 






View attachment KerrLab Automatic Electro Melt.bmp


View attachment Vacuum EZ-CAST.bmp


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