# Rubber Deterioration on Brass



## Tex-Shooter (Dec 17, 2009)

I discovered something quite by accident this morning. Again I was rummaging around in some of my old slingshots and found the flip of Texas Charlie's that was given to me and I refurbished. The tip ends looked like they had rubber on them that had been there for many years and had not been cleaned off. I was puzzled to say the least as I was sure that I had put new latex bands on it. As I looked in the box further, I found the bands that I put on and the ends looked melted, but the bands were still good (see picture). I started to clean off the rod ends and found that the rubber on them was melted and almost like varnish, then it dawned on me! The flip was made with 3/8 inch brass welding rod and the brass caused the deterioration. I think that the lead content prematurely killed the live protein in the latex and caused this. Maybe some chemist could shed some more light on this, but it looks like Latex does not like brass. Also note that the Gum rubber that I used for the handle still looks fine! -- Tex


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## Viper010 (Apr 21, 2012)

live proteine in latex?? so how is it you can glad-wrap the stuff, stick it in a cool dark place for 20odd years n itl still be fine??

anyways, thanks for the heads-up Tex, i had 'planned' some frames fancied up with brass parts. i will now be sure not to put it in the forktips!

im with you though, any chemists that know the whens the hows n the whys about latex deteriorationg in contact with brass, please speak up!

cheers, remco


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## All Buns Glazing (Apr 22, 2012)

This is useful information - I was considering using brass rod for a TTF connection thing I saw here ages ago (sorry, citation escapes me).


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## Tex-Shooter (Dec 17, 2009)

I have some that is about 20 years old that has been stored in plastic. It looks good and feels good but does not shoot or act like fresh latex, but more like gum rubber. I also have some that has been in cellophane for about 40 years in storage and it will still shoot, but not very good or long. -- Tex


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## Tex-Shooter (Dec 17, 2009)

Charlie's flip had those bands on it about 2 1/2 years and was stored in a cool dark place. I think that brass is fine for a slingshot as long as you don't leave the bands on it too long, but shoot them up in a reasonable time. -- Tex


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## All Buns Glazing (Apr 22, 2012)

Got it


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## ZorroSlinger (Dec 12, 2012)

Among my other interests as a fan .... make-up type & mechanical prosthetic special effects (movies). They use raw rubber in liquid form and whip it up fluffy shave cream consistency & inject into molds. Practice is not to use bare brass metal (or similar like copper) directly against the latex material as it reacts with the metal. If they have to use brass metals in their mechanics, they seal it or wrap it in another material that does not react with latex rubber.


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## Pebble Shooter (Mar 29, 2014)

I already read about this somewhere at some stage: indeed, brass deteriorates rubber when both are in direct contact.

Brass is an alloy consisting primarily of copper and zinc, and a very small percentage of lead : it is the copper ingredient that appears to be the source of the problem i.e. rubber "melting", or becoming tacky when in contact with pure copper or brass. I found this useful info online:

"Effect of copper on crude rubber" - see here: https://pubs.acs.org/doi/abs/10.1021/ie50096a010

Thus, the fork tips of a slingshot frame should ideally not include copper or brass in them to avoid this problem.

More interesting background information on brass is available at Wiki: https://en.wikipedia.org/wiki/Brass


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## Island made (Aug 14, 2019)

I've tested this on my frames, (being primarily brass). Out of anything that I tried, the only band that I could get to cause a reaction is alliance #107's. So I've left a brass frame banded with 107 for over a year now, and the brass has tarnished slightly where it contacts the rubber. But no tarnish whatsoever under the latex ties, and the bands are still perfect. Actually shot it a few hundred times the other day. Maybe I don't have a problem because I don't actually use brass, but aluminum bronze. Less copper content and is actually much harder than steel. Have to cut it with carbide.













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## SLING-N-SHOT (Jun 5, 2018)

That's interesting Shane, but what's more interesting is that sweet frame, that is cool brother!
How'd you attach the antler to the forks ?

Sent from my iPhone using Tapatalk


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## urbanshooter (Aug 23, 2017)

Pebble Shooter said:


> I already read about this somewhere at some stage: indeed, brass deteriorates rubber when both are in direct contact.
> 
> Brass is an alloy consisting primarily of copper and zinc, and a very small percentage of lead : it is the copper ingredient that appears to be the source of the problem i.e. rubber "melting", or becoming tacky when in contact with pure copper or brass. I found this useful info online:
> 
> ...


Good shares! I have few cheapo slingshots from Aliexpress that have brass tips and I find the elastic discoloring where there is contact. However the bands don't seem to fail prematurely and not at those spots either. So, it's probably just more of a cosmetic annoyance than anything that would affect practical shooting or bandlife. I wouldn't store a brass tipped frame banded-up though. I just band it, shoot out the life of the band-set and then put it away till the next time. Haven't had any experience with better stuff like what Island made uses...


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## Island made (Aug 14, 2019)

SLING-N-SHOT said:


> That's interesting Shane, but what's more interesting is that sweet frame, that is cool brother!
> How'd you attach the antler to the forks ?
> Sent from my iPhone using Tapatalk


Thanks Darrell, I have a 5/16 steel rod counter sunk in the brass, then down through the handle for the strength. Then just 5 min epoxy to keep it together.


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## Ibojoe (Mar 13, 2016)

I must agree, that's a gorgeous frame Shane. I could not leave it alone for a year.
Actually a brazing rod is mostly lead and copper not a whole lot of hard brass content. The aluminum bronze has an entirely different make up (no lead and very little copper). I think If you would super heat it it would become brittle and not melt like a brazing rod. 
Besides if I can keep a set of bands on for a week, I'm lucky. Just my $.02


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## Island made (Aug 14, 2019)

Ibojoe said:


> I must agree, that's a gorgeous frame Shane. I could not leave it alone for a year.
> Actually a brazing rod is mostly lead and copper not a whole lot of hard brass content. The aluminum bronze has an entirely different make up (no lead and very little copper). I think If you would super heat it it would become brittle and not melt like a brazing rod.
> Besides if I can keep a set of bands on for a week, I'm lucky. Just my $.02


Thanks Joe. That's actually the very first 2 piece brass frame. Deer antler is very hard to come by here, because there's no deer on the island lol. I was making a skinning knife for someone and they gave me that piece of antler for the handle, well......I cut it to short. Hard pill to swallow, ya know being a precision machinist and all lol. They were fine with it and gave me another piece. Well I had this piece setting on my bench for a few months wondering what to do with it. Than I had a brass off-cut from a job, set it beside it. And bam there it was!!! The birth of the 2 piece frames lol.

Your exactly right about the aluminum bronze being different than the brazing rod. And the aluminum bronze being brittle if heated

Actually what I cut this piece of antler from is what I used on the olive chalice. Can't waste anything!!


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