13 posts in this topic

Just a question about rivets with copper stills. Is a joined seam of copper with rivets, functional to keep the sheets together and leak proof, or purely just decoration? Also, is the seam welded or soldered in addition to the rivets?

Share this post


Link to post
Share on other sites

With modern TIG welding (or MIG which I haven't used on copper) there is no need to use rivets, if they are used it is for decoration only.

If the joints are soft soldered I would suggest a few rivets as extra safety. Soft solder contains lead so it is not a good choice either.

Rivet heads on the inside of a still will retain moisture when the still is not being used. Copper compounds form in this moisture and you can get quite a buildup of blue/green that can't be good if it gets into the next batch.

A general suggestion for those who have a still that is not being used, open it up and dry it out. I have seen idle, wet stills, mine included, that start dripping blue liquid from the condenser (probably copper sulphate)

Share this post


Link to post
Share on other sites

The rivets will help to keep the seams together during expansion and contraction, but with a good solidly welded seam, that shouldn't be an issue. You can get lead free solder as well, just keep in mind it is only solder, and as such is a fairly soft metal, so as Pete mentions above, some rivets would be a good safety measure.

Share this post


Link to post
Share on other sites

So most people nowadays, just TIG or MIG weld things, and the rivets are for looks only, with a little retention in there for good measure. How about Brazing a seam? How does that stand up?

Share this post


Link to post
Share on other sites

brazing is pretty much silver soldering if you are talking about the same way that HVAC copper is brazed together, and the cost of that silver solder would make a TIG welder purchase really attractive...

Share this post


Link to post
Share on other sites

Braziing can be done with a torch using a flux and either brass rod or silicon bronze rod. It can be done with a tig and no flux with each of those rods. The joint does not have to be that tight. HVAC usually uses a phosphous copper rod with no silver in it or maybe a little bit. The phosphous acts as the flux. the tighter the fit the stronger.

Moe

Share this post


Link to post
Share on other sites

Here is what HVAC uses, 15% Silver...: $85 for 1lb... http://www.amazon.co...y/dp/B008AE4NBU

This is for copper to copper, brazing steel or other things you can use the other rods... but we are talking copper to copper, just like HVAC.

Firstly a question, what does HVAC mean?

Also, I assume the above rods are what we call "silver solder". I have mentioned this before, a stillmaker who gave me advice said that silver solder will eventually get holes in it when used in a still.

Does anyone know if this is correct?

Share this post


Link to post
Share on other sites

i dont know for a fact, but silver solder has lower melting point than copper, and stills can get hot. HVAC, is heating, ventilation, and air conditioning. You know AC dudes.

Share this post


Link to post
Share on other sites

I made a small 25 gallon pot still and heated it with direct fire propane. I used no silver solder, only soft lead free solder. I've run it many times and have never seen it ever get hot enough to melt the soft solder. My max temp ever at the still head has been 208f. I suppose if it were empty it would melt, but who would do that? Melting point of copper is 1,984f. Lead free solder melts at around 425f. Silver solder runs between a melting point of 1250f-1475f, depending on the amount of silver/phos copper. If you get a still that hot, you need to do some more research, or maybe shouldn't be distilling at all.

As far as silver solder getting holes in it, I don't know for certain. I've done many many searches for silver's reactivity with ethanol and have yet to find any info. Anyone?

Share this post


Link to post
Share on other sites

Hello Pete

First the term silver solder is used by so many people for such a large number of compositions that it becomes misleading to use the term. Some people refer to the alloy of 95%tin and 5% silver melting about 450F as silver solder or phosph copper which has about 6% phospher 0 to 15% silver the rest copper melt around 1200F to be silver solder others think it must have a min of 40% silver to be called silver solder. Alcohol does not cause pits in silver. Have who ever told you that alcohol causes pits in silver solder to explain what composition he is referring to. I have been working with silver solder making things for over 40 years. I use so much that I just make my own. I like 75% silver 19% copper and 6%zinc. It gives me the ductivity similar to copper so I can hammer curved shapes and anneal at 1400 and not reflow the solder, it is very strong. Now welding technology is so advanced that I Tig weld most copper that is 48 oz or heaver. My tig is a Miller inverter with pulser control.

Moe

Share this post


Link to post
Share on other sites

Good information there thanks Moe. The so-called "silver solder" I use for copper water pipes, has only 5% silver.

I will ask for more information about what type of silver solder he claims is pitted by alcohol.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now