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@Sheilajeanne I have no idea how bacon fat is different from pork fat - it is the same thing! Probably the smoking of bacon gives the fat that smoky fragrance as well. Neatsfoot oil smells unpleasant to me, but I like the use of it, so I use gloves when using it. If not, I feel the smell remains for hours, no matter how much I wash my hands. That is so true about processing fats. Everything is made, for the most, part, as it has been made for centuries, except for the packing and the exorbitant prices! I also plan to add mink oil to my list.

@fredk, no we don't need to mirror the experiments but they need to be similar and, like you said, probably will be. Animal fats like tallow, bear grease etc. I leave to others. At the most, I can do lanolin, which I do use in my leather conditioner anyway. @Sheilajeanne, won't bacon fat smell of bacon? So the leather will too. And an invitation to mice and rats?

@fredk Yes of course. A proper experiment. I don't mind your mentioning all the steps to take. It has been a while since I even stepped into a lab. Good to be reminded. I will measure and maintain proper documentation. Just a tad busy right now so will probably get everything set by Sunday. I have been investigating what is used to oil-tan leather - it is not really tanning as much as a treatment of chrome-tanned leather, where the leather is immersed in oils/fats. What I have discovered is that in earlier times they used to use fish oils but now use synthetic oils and complexes. I plan to call a leather store here to see if they can direct me to someone who can give me more information. Since oil-tanned leather is already well exposed to and impregnated with oils and waxes, our results will be skewed unless we know what is used, at least in the leather I use. So I will start with veg-tanned leather and do the oil-tanned leather if I get all the relevant information. @chuck123wapati welcome to the experiment. Tallow is something to which I do not have access, so that is a welcome addition, The surface on which the leather is kept will be a part of the documentation. I think, @fredk, once we have everything set, we could share procedures, so we all follow the same methods.

@fredk you hit the nail on the head. Incidentally, oxidation of oils produces peroxides as well as alcohols, aldehydes and ketones, among other things. Not what we expect to put on our leathers. Oils oxidize on contact with the oxygen in the air - they smell unpleasant, or not, based on the exact type of chemical produced. But just because there is no smell, it does not mean there is no oxidation happening; it just means that the products are of a type that do not have a strong smell; longer chain versus short chain fatty acids but that is going too technical.. It suggests that oils should be stored in air tight containers to prolong their lives. And maybe used lightly on leathers, except dry leathers which needs lubrication. Maybe some sort of anti-oxidant could be used as well. Need to look that up.

@fredk, good to hear about the leather in your car and other older cars. . It appears more and more likely that it is not the type of oil, per se, that damages leather. Engine oil, being non-organic, should last forever, like mineral oil. Organic oils are fine as long as they are not exposed to air over long periods. Even the olive oils that I hear were fine over 1000s of years, were in airtight containers. So air is the villain, it appears, specifically Oxygen. Wonder what the products of oxidative damage of oils are? Do they damage leathers? Lots of more research needed. @chuck123wapati yes it is. I wish more people would join in, with the oils and leathers they have and in their locale.

@Northmount, thank you. I will follow those directions on saving articles. I do hope we get more of them! @fredk About the hand-cream, I am increasingly starting to suspect that most oils do, not harm leather, per se, 'if judiciously used' - those are the operative words.. But then, there is oil tanned leather and how the oils in those leathers are affected by added oils. I am looking into that, a bit pressed for time though.

@fredk my area is rather warmer than yours. I'm in Georgia. I think you have a good plan. I should be able to do more or less the same. it's getting cooler here now. I plan to keep one set in the boot of my car; the 2nd in the garage which is always either very warm or very cold and dark, and the third set will be outside, exposed to the elements. My only concern is mold. I can take care of it if it appears but that will affect the outcome. I wonder if we even need to include thread. We know natural fibres break down naturally over time, regardless of treatment. @chuck123wapati there are, of course, plenty of variables that can affect the leathers. and we cannot include everything. But this is an effort to determine if the oils are, by themselves good, bad or neutral on the leathers. This very simple experiment will at least give an idea of whether the oils directly affect the leathers in any way.

I did not know we had a greater range. Hmm. I usually stick to veg tanned or oil-tanned. Both actually feel like leather. Oil-tanned is chrome tanned as well, with extensive oil or wax treatment and the results are pretty nice. Other chrome tanned, some do too but others are so plasticky, might as well use faux leather. I plan to only use leather which feels like leather. I doubt that any leather that is so coated with synthetic material that it feels plasticky needs much conditioning. Incidentally, I have some fractionated coconut oil - it is supposed to have less of an aroma than cold pressed. Could have fooled me! I applied a drop on my the back of my hand and it is already smelling strongly. Got it from Costco too. I wonder if the smell disappears after a while.

@Burkhardt, practical.

@Sheilajeanne I agree! About the description specially - idiots! And I like neatsfoot oil and use it, never mind what a lot of people say, I notice they are either company sites trying to push their own products or the know-it-alls - It takes all kinds. I'm always glad to hear good reports about it. It has been around and found useful for so long, how can it suddenly become 'not good'? Often, tried and tested are the best or at least as good. Wish it was a little less smelly though. I spoke to @Northmount about creating a repository and he suggests saving the files that people provide as pdf files. I am not sure how to do that here. Could anyone guide me on that or do it?

@fredk Yes that will be a proper way of doing this. I will be using coconut oil, food grade mineral oil, probably sesame seed oil and whatever else I have inside. I will need to check. I have veg tanned scraps, oil-tanned scraps and other chrome tanned scraps. I am trying to get some information on what oils and waxes are used to finish oil-tanned leather. The oils and waxes used in finishing oil-tanned leathers, might affect the results of additional oils. Do you know anything about it?

@chuck123wapati Haha. Can't comment on that. My dog chews her collars or tries to get them off to chew them, pulling until she somehow slips them off, then chews them. So no leather collars for her now. For some reason, she does not chew any of my leathers lying around, only her own collars. She knows it is hers, 'to do with as she wishes'. Smart!

Great @TomE. Thank you.

@chuck123wapati I certainly I did not know that, as many others probably do not either. All the more reason for a repository of knowledge. Besides, I am a little surprised at the general description of the oils. Usually in experiments, it is very specific and even if the results say the same, the actual items used are listed. It probably is, in the full article.

@TomE It is clear that synthetic fibres survive well over time. Thank you, each person's information adds to confirming this. And having a reference section is such a good idea! We have a proverb in Hindi which says, roughly as follows: "What can be done tomorrow can be done today; what can be done today can be done now" Going by this, maybe those of us who find good articles can contribute and request the forum to make it available to everyone. We can start with yours, @chuck123wapati, if you do not mind. Now how does one go about requesting the forum to have a section for a repository of such knowledge or is there one already to which a section can be added?

@fredk I bought most of my thread based on diameter and color and do not know what it is made of - probably synthetic, since that is what is mainly available everywhere these days. I took off all the labels as well unfortunately. So I will need to look for cotton or linen. I don't mind though,. It will be an interesting exercise. If your synthetic thread was strong and stable so many years later, that is evidently not the problem. I have not heard about anyone else complaining of synthetic fibres breaking down either. So that narrows it down to the leather itself and natural fibres. Your experience with linen thread, so similar to mine, suggests it is the thread itself which deteriorates over time, naturally, rather than because of anything applied to it. I wonder why not all leather goods made with natural fibres deteriorate though. Well waxed and therefore protected maybe? Or maybe the stitching itself is the issue too? Too tight, too loose, I'm afraid I cannot help there. Does anyone have any idea about this?

@chuck123wapati, the article you have given shows the effects of fats soon after tanning, not the effects of long-term use of it by the users of that leather. The article also talks about how synthetic oils have superseded natural ones because of oxidative issues. But it does not say exactly which fats and oils and what the effects are over a long time, Although it does say the actual type oil does not matter. It matters to us though. All of us here are talking from personal experience or trying to get personal experience and are curious to know, once and for all, about the true ill-effects or advantages, or both, of oils commonly used by ordinary leatherworkers. If you do have actual knowledge it would be nice to hear about it, like so many others have so beautifully and positively contributed to this thread.

@kgg and better smelling too.

The deterioration of leather and the thread happens over time. I I will apply the oils on the leathers and keep them somewhere safe, and check through the months, with periodic updates if there is damage. @fredk what do you think? Incidentally, does anyone have natural fibre threads that have deteriorated without use? I know my regular stitching thread does so, and I have no reason to expect otherwise from thread used for leatherwork.

@ScottWolf that is exactly the point @fredk made earlier, that people blindly repeat what they have heard, not necessarily from their own experience. If you wants to hear the actual voice of experience, you need to have worked with leather for years and remember what was used, several decades later, to know what was or was not detrimental to it, and there are so many other factors that can damage the leather as well. I, for one, am too new to leatherwork and will be long dead and gone before many decades have gone by. Ergo my comment about instructions in my will. It is not a matter of refusing to acknowledge information as much as the widely present views of today - " I saw it online, so many people online said it, so it must be true. Even if you say different, so many online say so, so I believe them'. About oils turning rancid, it is the smell or texture that is unpleasant most often. Besides I do not know what the products of those oxidative processes are and they may affect the leather, or not. Additives will retard or prevent the oxidation of oils but then, you have to have the correct proportions of the additives for preservation, else it is pointless. That becomes another chemistry experiment. I should think anything used in excess would cause some issue or the other, excessive softness or even remaining on the surface causing greasiness. Like you said, most commercial products, if you read the MSDS, contain many of these oils and waxes . I have been reading them up when researching leather conditioner recipes. It is a little amusing when people refuse to use neatsfoot oil or mineral oil or petroleum products and then swear by products with these very ingredients. One thing I have noticed is, when people say that leather deteriorated, it is often the threads which rotted away. Natural fibres deteriorate faster than leather, naturally. That happens even in ordinary cotton clothes with cotton or linen thread. Cotton and linen themselves deteriorate over time. I wear a lot of cotton and some of my favorites are not usable 20 years later. That is all the time it it takes. No one uses any oils on ordinary clothes! Leather itself falls apart sometimes but I suspect that is because of excessive oils or the way it is used. Not knowing what causes the damage, the easiest to blame is the oils used. Commercial companies with ulterior motives push this further and a myth is born. To debunk this, our experiments with leather might help just a little. Putting in a few stitches with cotton and synthetic threads is a good idea. @kgg that is good information about jojoba oil. It is said to have a composition similar to skin oils. You are talking from personal experience. @Burkhardt which vegetable oil do you use? I hope others join @fredk and me in this experiment, using oils and scraps they have at hand. About mice. Please don't remind me. My cat caught one and placed it behind me on the sofa. It fell behind the cushions and I found it a while later while cleaning. It has nearly petrified within a few months. Evidently in that place it was deprived of air. Not a pleasant experience. Mice will eat anything and are smart too, and cute. I always hear people squealing about their cuteness - does not deter from their unpleasant pee and stealing and chewing habits! I believe the smell of cloves deters them.. No idea if that is true and I do not I want my leathers to smell of it.

@fredk unfortunately, you are right about the reasons for research. About the olive oil, exactly. Exposure to air.. and leather is not going to be kept air-tight! SO great. I will try as well. I have plenty of scraps I can use. I have coconut oil, both fractionated and cold pressed. I know the cold pressed goes rancid fast if exposed to air. So will not use that. I know how it smells. YUCK! Will check the fractionated. Use it on veg tanned leather and keep it outside, in a warm place for a week to 10 days, reapplying if it gets too dry. Let's see what happens. Cold pressed coconut oil gets smelly in a few hours. I suspect this will too. People use fractionated coconut oil in their hair as an after wash conditioner - you can smell it from a distance.

@dikman exactly what I think too. Companies will go for what is cheapest. And Mineral oil is obtained fossil fuel, therefore organic or 'natural'. That is what those companies probably mean. And fool a the majority of their consumers. @fredk WOW! Your Austin will be a 100 soon! Pics please, if possible of this car? Back to topic, You are perfectly right. Tanneries and most everyone else will parrot what is online. And from your experience, engine oil does not damage leather. So mineral oil should be fine too. @TomE's and @sheathmaker's experiences show that neatsfoot oil, used judiciously, is also good for leather and not does not damage it. SO mineral oil and neatsfoot oil are good possibilities for use in conditioners. Both evidently do not do any damage. I wonder if there are any labs doing some sort of research work on the effects of other oils on leather. Vegetable oils, I am a little concerned about. By their very nature, they are not meant to have a long life or survive differences in temperature; how long do coconuts or avocadoes or olives survive anyway? In contrast, cattle have longer lives and are warm-bodied. I'm probably talking through my hat though. I feel there will be someone or the other telling me so, usually kindly. You have a good idea @fredk Maybe as many people as possible could talk about their experiences here, rather than hearsay off the internet, about the effects of different oils on leathers, in different conditions. A repository, so to speak.

@TomE, @sheathmaker I like neatsfoot oil too and use it all the time. After all, it has stood the test of time. The smell however, is sometimes a bit unpleasant. It also darkens leather and I want to make a conditioner that will not do so. Ergo, the questions about mineral oil.

@Gump, Thank you. I will look for it.

@ScottWolf I have discovered that mineral oil makes leather shine. I was not sure of the sealing properties but that becomes icing on the cake as we use it last when getting a shine anyway. @fredk Could motor oil have other additives perhaps that cause the damage? @Wepster PB Blaster will surely have other additives. Could they play a role in the damage? As @Klara says, the composition could make a difference. @TomE, @fredk - difference between living skin and preserved skin - therefore different requirements in care. Of course. But I suspect mineral oil is relatively inert on skin and only prevents surface dehydration. But it might react with chemicals in leather which has after all undergone chemical modifications. There are supporters and nay-sayers for every single oil online, from neatsfoot oil to mink oil, to vegetable oils. I suspect leather deteriorating is a result of several factors including but not limited to the oils used. I guess it is a matter of not just what but how much, like your example of neatsfoot oil @TomE @Wepster I believe there is a tannery around here, if I remember right, of exotic leathers. But leather anyway. I will inquire with them.. Put it up here as well, if I learn anything. Thank you everybody for all this information. I am going ahead with making a conditioner with mineral oil - what I have is food grade. If the leather deteriorates over time, I will leave instructions in my will for that information to be put up here.