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I have talked elsewhere about using ethylene oxide to make safe an old violin that had  had too close an encounter with mice and might have been a Hanta Virus risk. Recently a friend mentioned that his two performance violins had been exposed to damp conditions and mould had been found inside both violins. One is an old Italian and the other a contemporary violin by a European maker. We discussed treatment and investigated Ozone (not effective enough against mold spores) and various other options and concluded that The Ethylene Oxide method would likely be the best route, but I was a bit nervous about putting a very valuable instrument through the gas.

Everything suggested that all should be well, but in order to allay my concerns we gas sterilized a couple of less valuable violins with oil finishes as a warm up. That gave us n=3 and with only a little trepidation we ran the old Italian through a 12 hour cycle today. As expected (but still much to my relief) everything went well, the violin came out as beautiful as it went in (and also less moldy).  Unexpectedly, the label which was almost illegible from the ravages of time and black mold came out of the sterilizer looking like a museum conservator had spent weeks restoring it. I have no explanation for the label, but just wanted to let you all know that this is a very viable method of sterilizing and making safe a violin that has been exposed to such adverse events. 

Ethylene Oxide sterilizers are fairly common pieces of kit in the veterinary and medical worlds if anyone has a need. They are not expensive to run and they certainly do a good, safe job. Tomorrow it is the turn of the Contemporary European instrument.

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I've seen this type of black mold before in instruments, and have always wondered how to sterelize it. Taking the top off is not worth doing for something like this IMO, so I'm glad to hear of your success. What does the inside look like and where does the mold go? Does it remain in the instrument? Do you have photos of the label? Keep us updated!

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From the CDC website:

"The main disadvantages associated with ETO are the lengthy cycle time, the cost, and its potential hazards to patients and staff; the main advantage is that it can sterilize heat- or moisture-sensitive medical equipment without deleterious effects on the material used in the medical devices (Table 6). Acute exposure to ETO may result in irritation (e.g., to skin, eyes, gastrointestinal or respiratory tracts) and central nervous system depression.859-862 Chronic inhalation has been linked to the formation of cataracts, cognitive impairment, neurologic dysfunction, and disabling polyneuropathies.860, 861, 863-866Occupational exposure in healthcare facilities has been linked to hematologic changes 867 and an increased risk of spontaneous abortions and various cancers318, 868-870. ETO should be considered a known human carcinogen.871"   

You need to be really careful with that stuff!



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12 hours ago, JRyn said:

 What does the inside look like and where does the mold go? Does it remain in the instrument? Do you have photos of the label? Keep us updated!

Good question. I had expected that the mould would be killed and the spores inactivated but expected no change in the appearance. The process flushes and purges the chamber repeatedly with clean air every two minutes for two hours at the end of the cycle, so it might be that the mold is literally vacuumed away after being killed? The sterilization is by alkylation: any chemists out there know if that might have had a bleaching effect on the mold?  No photos of the label I'm afraid. We were both so relieved everything had survived unscathed, we kind of bolted out the door and went home to our beds.

There was a paper from the nineties that confirmed ethylene oxide did not damage woodwinds or stringed instruments but somehow it was hard to trust rationality when using it on very valuable instrument!

1 minute ago, FiddleDoug said:

Absolutely. We use one of these . The process is as follows. The instrument or surgical pack, endoscope or whatever, is wrapped to protect it from scratching and placed in a heavy duty plastic bag along with a sterilization indicator, and a humidichip to maintain humidity along with a multiwrapped ampoule of gas. A purging wan is placed inside the bag and the bag is gathered around the wand base and secured with a very tight Velcro strap. The whole assembly is then placed inside a sterilization chamber and the air in the bag is purged by a negative pressure applied through the wand. The ampoule is then manually broken Within its carboard over wraps and the door of the airtight chamber is then locked. The gas fills the sealed bag which is contained within a sealed locked container which cannot be unlocked or opened for the next 14 hours. The instruments then sit in the gas for 12 hours. After 12 hours the machine vents the gas via an exhaust tube that goes through post treatment depending on your state or federal rules. The bag is then flushed and purged with fresh air every two minutes for a minimum of two hours before the door can be unlocked. 

Using this method the risk of exposure to operators is as close to zero as can be reached. 

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3 hours ago, FiddleDoug said:

" We use one of these"

Not something that most of us would have in the basement :D , but it could be an interesting and valuable tool for certain cases. Thanks for the info.

If you ask around local specialty vet hospitals you will likely find  someone who has one and usually we are pretty easy to get on with folk. Aside from being in Canada which would complicate shipping, I would be happy to help out anytime someone has a problem instrument that needs treating.

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Ethylene Oxide will go anywhere that air will go. The limiting factor would be cycle length. The narrower, or longer, more blocked a channel is, the longer it would take for the gas to diffuse into the channel and reach adequate concentration. Sounds like a research project for someone.

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I am not a luthier, but I am a chemist. Ethylene oxide is a very powerful alkylating agent and I would be quite concerned with potential irreversible effects on wood, varnishes, and glues.

Effect of Ethylene Oxide Sterilization and Accelerated Ageing on the Physical and Mechanical Properties of Beech, Oak, and Elm Wood: Part 1

Effect of Ethylene Oxide Sterilization and Accelerated Ageing on the Physical and Mechanical Properties of Beech, Oak, and Elm Wood: Part 2

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These are two really good papers. I don't have to hand the work from the nineties which was, I think, a patent application, but that included some information about safety to varnish. My current crop. Two contemporary oil finished violins, two dutzenbeit and one old Italians, have suffered no damage to their finishes.

It's a pity these papers did not look at violin plates and ribs. We have something unique with what are effectively thick veneers that are finished on at least one side and sometimes sealed on the other. 

If anyone wants to do a research project using some finished plates and ribs I would be delighted to cook them up.

Meanwhile, according to the ear test, there is no difference between  pre  and post treatment sound. 

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