How "not' to kill mold spores, and the right way

[DonVoigt]

This is a tough thread to write and a super-cautionary tale!

I recently bought an Artillery holster in nice shape at a good price,
1917 marked, belt converted, nice supple leather. Had Jerry the holster man take a look at it before I bought it, looked fine, except for some white mold spores.

Asked the best way to "kill" the spores and got instructions:

"Heat oven to 350 degrees, put holster on a cookie sheet and put in oven at 350 for 5 minutes, cut off the heat. Leave in for one hour and take out. Mold will be dead and no harm to the holster."

Simple, just be aware that it may smell up the kitchen a little.

So me, I think well I'll take care of that and wrap it in foil to keep the odor down and prevent it drying out to boot.

WRONG!!

What I did was "boill" the leather , then dry it out! It was shunk, twisted, and hard as a rock, in short RUINED! Only salvageable
piece was the brass stud for the cleaning rod flap.

I'm not posting this so anyone can tell me I was stupid or dumb or anything of the sort, I have already beat myself up enough.

This is to help someone else avoid a potential disaster!

I asked Don to post this for the reason he has stated..I recommend this procedure to any and all collectors who have a mold problem on leather. My Wife Ellie and I struggled for some time many years ago to find a cure/solution to some molds found on Luger holsters. After much research on mold, we concluded that if enough heat could be safely applied, the mold spores deep down in leather would be killed. We did extensive testing..with old leather parts and pieces that if ruined..would be no great loss. And ruined they were. I had this very thing happen to me when I put leather into an enclosed bag and applied heat.
What happens in an enclosure is that molecular moisture..present in a fairly sizeable quantity in a holster, escapes and condensates inside the enclosed area and turns to steam. Steam is deadly to leather. Just as it is to living skin. I can't tell you the chemical or physical properties that cause it to change..I only know the result as you can see from Don's photo's. Disaster on a grand scale.
The basic heat treatment WITH NO enclosure other than the oven..works with NO HARM to leather. I have done it more times than i can remember. 350 F. for the short period recommended will NOT dry out leather. It often has the opposite effect. Moving and distributing any applications of whatever has been put onto it over the years. I have NEVER had a bad effect yet by placing a holster in an oven at 350, laying on a cookie sheet with no covering whatever.
One caveat comes to mind as I write this..LEATHER. I have NO experience with this procedure for ERSATZ holsters or say, Japanese CANVAS holsters. LEATHER ONLY.
So to clarify this procedure..that I have used with great success to kill some types of mold and completely erase the white mold flowers from the surface.

Preheat oven to 350 F. Place your leather item on a foil covered cookie sheet..foil is just to make the Wife happy. If you are a bachelor a plain cookie sheet is fine. I have never had anything drip off.
Place your cookie sheet with exposed leather on a middle rack. I sometimes use a wooden stick to prop open a Luger top so the heat can reach full temperature inside.
I usually wait a few minutes to make sure the oven has achieved 350 after opening the door..then TURN THE OVEN OFF! Let your leather lay..an hour is usually long enough. The oven will gradually cool but the leather will have reached killing temps through and through. I have found no harm to studs or buckles..One benefit has been to take out your leather while still warm and verdegris will easily wipe off with a terry rag.
As horrible as this experience has been for Don and even myself..I encouraged Don to help us all with an explanation of what can happen..these photo's are tragic..but there IS an explination of why it happened and we should avoid this, learn from this. I wouldn't FEAR my mold killing procedure..just DO NOT ENCLOSE the leather, leave it EXPOSED.
Thanks Don, I know it's a platitude..but your loss results in our gain. Learning is an ongoing endeavor.


Before and after disaster:

[kurusu]

I'm sorry that such a thing happened.
Got one question though. Do you know for sure that if you followed the instructions to the letter the outcome would be different?
I think I would try first with a worthless piece of leather.

[ithacaartist]

A sad tale, for sure. We feel your pain.

350 degrees is a dangerous temperature to work with. Anything organic left in this environment will resemble a black potato chip if it's in there long enough. Wouldn't 160 to 200 degrees be effective for killing mold?

A spray with 1/2 vinegar 1/2 water and a quick wipe should kill your spores. Treat the surface only, don't soak.

[John Sabato]

How terrible Don... what a tragedy... my condolences.

[Jim Solomon]

Don,
So very sorry that this happened to you. However, as further evidence of your respect for and contribution to this great Forum, you choose to share with us in hopes of helping others to be aware of the danger of the procedure which you tried.
Thanks,
Jim

[lugerholsterrepair]

350 degrees is a dangerous temperature to work with. I beg to differ. It has been tested and proven over the last ten years to be safe and effective used as directed. 350F will not ignite paper. 350F is what it takes to kill the encapsulated spores buried in the interior. The lessor temperature of 160 to 200 will erase the mold flowers..the stuff you see on the surface but you have to remember our mission..to KILL and further reduce another outbreak. A spray with 1/2 vinegar 1/2 water and a quick wipe should kill your spores. Should? The spores are NOT on the surface. They bury themselves..with a spray with 1/2 vinegar 1/2 water and a quick wipe you MISS all the parts you miss..it's unavoidable and IMO this solution is not a proven mold killer and eradicator. You can wipe with a dry cloth and wipe away the flowers. This too is inefective and may even be spreading the problem.
A spray solution is also liable to discolor or stain light colored leather..turn it splotchy. Even plain water will do this. So it's not anything I would do but I hesitate to discourage you from something that works for you.
My heat treatment has NEVER failed me. It has always worked with no damage providing the leather is left exposed, NOT enclosed.
One thing I will say about it though because I am a student and always wanting to learn. Mold does on occasion return. I cannot for sure attribute this to it migrating onto a clean holster or some spores remained alive? I have some holsters that seemingly you cannot keep mold off. Japanese holsters are particularly vulnerable.. Something about these attracts mold.

[George Anderson]

I use straight vinegar but wonder if freezing might work just as cooking does but without the possible over cook.

[lugerholsterrepair]

George, Your normal home freezer will not adequately freeze ice cream. The mold is an encapsulated spore. It is resistant to pretty low freezes. I am no scientist but I would think the temp might have to be lower than most homes are capable of to have any chance for success.

[ithacaartist]

Originally Posted by lugerholsterrepair

My heat treatment has NEVER failed me. It has always worked with no damage providing the leather is left exposed, NOT enclosed.

Jerry, I must concede most of my suggestions are probably more appropriate for something other than holsters, except for the outside of a black one! Although the actual ignition of something in the oven would not quite happen at 350, stuff left in for extended periods winds up black/brown. Everything that gasses off up to 350 will be gone.

I think the success of your method is the two key factors of your instructions: Five minutes, and exposed. I found the chart below, along with some more general discussion of mold. 350 falls somewhere between incineration and an autoclave, but all the times listed are much longer for lesser temps. Your method appears to give a deadly dose of heat to kill the spores, but not so long as to cook off the leather's volatile components--just long enough to "heat it through".

Table 1. Recommended use of heat to control bacterial growth (degrees Celsius)

Incineration >500o Vaporizes organic material on nonflammable surfaces but may destroy many substances in the process

Boiling 100o 30 minutes of boiling kills microbial pathogens and vegetative forms of bacteria but may not kill bacterial endospores

Intermittent boiling 100o Three 30-minute intervals of boiling, followed by periods of cooling kills bacterial endospores

Autoclave and pressure cooker (steam under pressure) 121o/15 minutes at 15# pressure kills all forms of life including bacterial endospores. The substance being sterilized must be maintained at the effective T for the full time

Dry heat (hot air oven) 160o/2 hours For materials that must remain dry and which are not destroyed at T between 121o and 170o Good for glassware, metal, not plastic or rubber items

Dry heat (hot air oven) 170o/1 hour Same as above. Note increasing T by 10 degrees shortens the sterilizing time by 50 percent

Pasteurization (batch method) 63o/30 minutes kills most vegetative bacterial cells including pathogens such as streptococci, staphylococci and Mycobacterium tuberculosis

Pasteurization (flash method) 72o/15 seconds Effect on bacterial cells similar to batch method; for milk, this method is more conducive to industry and has fewer undesirable effects on quality or taste

[lugerholsterrepair]

David, Thank you for some insightful input! Yes..the time IS very important. I have had some "heated" discussions with my lovely Wife about this..She says to place the leather into an oven that indicates 350 F and immediately turn it off. I say opening the door to place the tray and leather colls a few degrees so leave the oven on a few minutes THEN turn it off. I am not sure it makes much difference but I have a useless piece of leather I can use for a test. I will place it in the oven and bake for say what? 15 or 30 minutes? To see the effects of the cook off the leather's volatile components-It will be interesting I bet! I will report back if I havn't burned down the house...

[ithacaartist]

Jerry, also try the temps 60-70 C for the 30 minute time. I'm curious to see what that level of heat/time does to a sample. If one were to put a dinner plate of food in for 10-15, it would be nicely heated to eat. I'm wondering about the variables of too-done food--one thing different might be that there's lots more oily component in food, which helps it brown. Leather would have lots less.

BTW, I spent a little time on the Horn (cow, not musical) Forum a while back, while getting info about making a powder horn for my son. I don't think you will get in anywhere as much trouble with the wife as they do with theirs when they simmer up a batch of "horn soup" to soften them (horns, not wives) for adjustment!

[lugerholsterrepair]

Jerry, also try the temps 60-70 C for the 30 minute time. David, you will have to speka da English. 60-70 C is this some foreign tongue?

Yeah..boiled horn, I bet it smells yummy! Some things you just have to do in the back yard!

[Edward Tinker]

I toyed with making walking sticks, still like it, tried to do horn, you have to soak in boiling water, too much and it gets soggy - I imagine just like too much heat...

so, was I supposed to vote #2

[Sonofeugene]

A little internet sleuthing tells you that you don't need to go nearly as high as 350F to kill mold spores. But you do need more than 5 minutes. Much better to go longer at lower temp than shorter at higher temps.

Keep in mind that your typical oven doesn't cool off that fast once the heat source is turned off. It can remain very hot for a long time.

Bummer about the holster.

[lugerholsterrepair]

Much better to go longer at lower temp than shorter at higher temps.??? How low and how long? A little internet sleuthing tells you that???? Tells you what?

[ithacaartist]

This idea is evident in my chart--quicker, hotter or slower, less hot. Jerry's scrap-strip experiment will settle the issue. Hey, what about the microwave oven?

Originally Posted by lugerholsterrepair

David, you will have to speka da English. 60-70 C is this some foreign tongue?

OK, I'll do the calculations just this once. I don't bother estimating by conversion formula any more, just use a search. By the time I had typed in "60 deg", a list of suggestions popped up and the answer was one click away. 60 C = 140 F, 70 C = 160 F. Also, the standard temp for sterilization is 121 C (250 F). Length of time is also a factor, measured as The Thermal Death Time, which is different for different organisms. From the Mushroom Forum (http://www.shroomery.org/forums/show...umber/11563238)

An example to clarify:
Assume the TDT for a certain bacterium is 1 minute at 121 °C, and you have 1000 of those bacteria in your jars.
After 1 minute at 121 °C, you have killed 900 of them (90%).
After 2 minutes, you have killed 990 (99%) of them.
After 3 minutes, you have killed 999 of them and have one left (on average).
After 4 minutes, you have on average 1 bacterium in every tenth jar.
After 5 minutes, you have on average 1 bacterium in every 100th jar. And so on.

There is no specific temperature at which contaminants die, it has to do with time as well.

Mold spores are everywhere! Flies deliver them via the hairs on their legs! Strictly speaking it is impossible to kill them all, or prevent them from access to all but a permanently sealed environment. All we can hope to do is keep them from germinating and growing by maintaining materials in a cool, well-ventilated, dry place. (Something tells me Jerry already recommends this!)

Mold can affect all organic collectibles! A decent article, "Mold is Not Your Friend" https://www.imagepermanenceinstitute...old-not-friend

[lugerholsterrepair]

David, Thank you VERY much! I must admit I am a minimalist. Find what works..don't Einstein it..let it run. This subject however does deserve some fine tuning. I believe the heat method is safe and effective. IF the heat can be lowered I can only surmise this would be as effective if the time involved were lengthened.
I appreciate your calculations..I use F not C and I use standard measurements not metric. I only use metric for my carpentry. I find it is much more sensible when building bird houses!
When I get a little free time I will explore your links. I am certain they will be fascinating!
Thanks..
Jerry

[hayhugh]

Yep, my oven dial is in F not C also.......

[saab-bob]

Just want to put out a kudos for Jerry on this mold issue.
I had been storing my holsters in a couple of sealed plastic containers out in the garage for years. Never had a problem till about 6 months ago. I went out to do my quarterly wipe down and found white mold spores on about 80% of my leather holsters! Of course,the item most effected was my dads 1911 rig he carried in WW2.
After doing some research, the most mentioned cure was the vinegar mixed with water in a spray,as David described. After testing on a inconspicuous part of a vintage holster,it turned the leather darker and roughened the surface of the leather. No good.
So I contacted Jerry for some advice. He was very gracious and gave me his oven heating method. Since I had a bunch of holsters to process he suggested heating the oven to 350 degrees and putting in a cookie sheet of holsters for 15 minutes,remove and repeat.
Long story short,it worked great. None of the holsters where effected. The mold magically disappeared. I did have to bake one holster twice.About 2 weeks after the first bake the mold came back,but only on 1 side. That side was against the cookie sheet and I surmise that side didn't get enough heat. After 2nd bake,with the holster propped up for better circulation,mold still gone after a few months.
I also sprayed the vinegar water solution on all the containers and lids and anything else that might have been contaminated.
I now have most of the holsters in the house now and check them every few days,no sign of mold!
Thanks again Jerry
Bob

[tomaustin]

saab, do you know what changes occurred in the previous storage location in the garage? after many months, here comes the mold...any ideas?? thanks, tom