Mineral oil bad for leather? Or good? Or neutral?

[fredk]

I'm actually having difficulty getting chicken fat/grease. All our chicken is extra lean and don't provide as much as a couple of grams

[SUP]

I could try the chicken fat thing. Exactly how do you use it? Just render it in a pan and use that?

[fredk]

More basic than that. My intention is to replicate what my friend had and did.

A medium sized draw-string bag of thin veg tan and a leather lace

The chicken fat/grease was taken from a cooked chicken. The cold fat was liberally applied to the bag and excess wiped off

The bag was kept in with his other kit, so it was warm and dry

I'm not sure how long between applying the fat/grease and it started to go rancid and how long until he brought it to me

My friend did this as the 'expert', who taught him to make the bag, told him to as it would water-proof it and 'thats what they would have used' (in medieval times)

[SUP]

God save us from experts!😅

I think i can replicate that. Makes it easier for me. I make my dog's food every few weeks with chicken. She dislikes all other meats. So when I cook the chicken, the fat of course floats on top and I can use that. 

The boxes I have will be nearly airtight which might not replicate either your friend's experience or that of the woman whose bag I worked on. Maybe I should keep several pieces inside bags in dry, dark areas, enclosed but not air tight. Maybe thick brown paper bags. I think I will try both, in the tins and in bags. Let's see which stinks more.

I will also test some vegetable oils known for going rancid. 

[dikman]

Fred, I just threw away a litre container full of chicken fat - how do you reckon I would go sending it to you in the mail? 

Seriously, I wouldn't ever consider using chicken fat on leather unless you have no sense of smell!! It stinks to high heaven and is a sickening smell!

[SUP]

@dikman exactly! But let's see, who knows? I get a load of it every fortnight or so. It probably stinks because of attached proteins. Using clear, pure fat might be different. We can always try.

[AEBL]

For stinky oils - you could try "sparging" it ... get an aquarium bubbler (little pump with a stone at the end that emits tiny bubbles) and run that for a while. I know for less viscous things, say in the olive oil area of viscosity, you can remove smells a bit. Sometimes it takes a day or so, and for shmaltz (chicken fat), you might have to sparge it in a slow cooker.

I have only sparged less viscous things like Copper Chloride etchant ... you might also have to worry about foam, so if you try it, don't try it with a full container ... try half full for starters.

Edited April 10 by AEBL
one more thing

[SUP]

On 4/10/2025 at 9:04 AM, AEBL said:

For stinky oils - you could try "sparging" it ... get an aquarium bubbler (little pump with a stone at the end that emits tiny bubbles) and run that for a while. I know for less viscous things, say in the olive oil area of viscosity, you can remove smells a bit. Sometimes it takes a day or so, and for shmaltz (chicken fat), you might have to sparge it in a slow cooker.

I have only sparged less viscous things like Copper Chloride etchant ... you might also have to worry about foam, so if you try it, don't try it with a full container ... try half full for starters.

I'm sorry for the delayed response.

 I just made a batch of dog food and I do not have sufficient fat to 'sparge' it. I'll probably put it off until winter. It is hot here so I do not want to keep it indoors.  Outdoors, in the heat, it will really stink.

On an aside,

I discovered that wax really darkens leather, even more than any of the oils. In another thread, I have explained how I dipped a piece of split that I normally use as a pounding board, into melted wax and dried it. I use this as a pounding board now - hard enough but does not damage the tips of my tools and the wax constantly lubricates it.

The leather is hard and so much darker, it is now a dark medium brown. it started off the light color of veg tanned leathers. 

[fredk]

10 minutes ago, SUP said:

I'm sorry for the delayed response.

S'alrite. I've done nothing lately.

But I've cooked a chicken and I've plenty of fat

12 minutes ago, SUP said:

. . . In another thread, I have explained how I dipped a piece of split that I normally use as a pounding board, into melted wax and dried it. I use this as a pounding board now - hard enough but does not damage the tips of my tools and the wax constantly lubricates it.

This was one of the ways that leather armour was made, from the early Roman times up to the 19th century. see cuir bouilli, 

[SUP]

26 minutes ago, fredk said:

This was one of the ways that leather armour was made, from the early Roman times up to the 19th century. see cuir bouilli

Oh! Nice. New use for old techniques.

28 minutes ago, fredk said:

S'alrite. I've done nothing lately.

But I've cooked a chicken and I've plenty of fat

I have a little, flavoured with pumpkin and carrots, asafoetida and turmeric, and garlic. So I cannot use it. I forgot and added all the ingredients to the chicken when cooking it.

Next time, I'll try to remember. 

[fredk]

I meant to post this a couple of weeks ago

I got a piece of veg tan and smeared it in chicken grease/fat. Not too much, just a good coating with excess wiped off.

It didn't last a week!

It was really rotten to smell and so sickening I didn't bother to see if the leather was affected by the rancid chicken grease/fat

Meanwhile, back at the ranch;

No changes to any of the other test pieces, except a slight lightening (bleaching out) of the darker pieces

I'll do a 'proper' report at the weekend

[SUP]

I wonder whether that (the smell) happens because the chicken grease is not purified? Everything else that we have used is purified with no proteins remaining. It is, after all the proteins that putrefy  and cause that awful smell. I wonder if there is a way to purify chicken fat. 

I think I will put off that experiment until I learn more about it.

Edited June 6 by SUP

[dikman]

Told you so!  I have chicken fat in my BBQ at the moment, now that winter has started it solidifies into a nice-looking fat but as soon as the weather warms up it goes runny like water. It also attracts the European Wasps, which have difficulty swimming in it! 

It's the last thing I would ever put on leather (thinks: pictures person with leather purse running down the street chased by hungry wasps! ends thinks).

[SUP]

@dikman you're right. Plain chicken fat is not purified and has things other than fats in it. So putrefaction and the accompanying stink happens. But what about absolutely purified chicken fat? Although I have no idea how I can do that, unless I cook the fat until all the non-fat components get fried and turned to coal and I strain the oil and use that. 

[dikman]

You're talking about the same process I use to make tallow (I use a slow cooker over several hours). It might work, maybe, but I'm not interested enough to try it. I think either you or fred should give it a go, seeing that this is primarily your thread () and then we'll all know.

Pictures come to mind of SUP leaning over a big cauldron of simmering chicken fat, stirring regularly. 

[SUP]

A big witch's hat (leather, of course) and grubby black robes. Surrounded by mounds of chicken meat and feathers. Think how many I will need to slaughter to get a CAULDRON of fat! All the area cats and dogs and rats surrounding me as well. Hmm... Halloween comes to mind. What an idea.😆

I will probably try to render some chicken fat  sometime soon. The next batch of dog food is nearly due. Hope it does not smell too much. The dog food is bad enough.

 

[fredk]

12 hours ago, SUP said:

. . .  But what about absolutely purified chicken fat? Although I have no idea how I can do that, unless I cook the fat until all the non-fat components get fried and turned to coal and I strain the oil and use that. 

How do I/we do that?

I know the first step is to cook me a chuck to get the fats

[dikman]

Searching with google turns up several methods of "purifying" chicken fat, one of them refers to "degumming" the fat using phosphoric acid and then adding lye to balance the ph and to help form the "soap" that is skimmed off.

Most seem to refer to a similar process to making tallow, slow cooking the fat and some say to then add boiling water to separate the gunk for skimming off. I would rather use the process to make tallow as I know that works and it stores indefinitely with no rancidity.

Here's a thought, perhaps if you go to your local roast chicken shop I'm sure they'll be happy to give you a few gallons of chicken fat. 

[SUP]

Just watched a YouTube video about using just the skin, gently cooked in a pan until the fat is rendered and then straining it out. Nothing else added to it, so  the final liquid is pure oil. I will probably try that. 

 

[SUP]

The method I described is to make 'Chicken oil' which is used as a flavoring agent in far-Eastern cuisine. There are several ways to make it but this seemed to me to be the most suitable for our purpose.  Cleaned chicken skin heated in a clean pan until the fats are rendered. Only fried skin remains so I presume the oil will be pure.

[AEBL]

I'll bet that there will be water in whatever you're rendering from the chicken fat. The easiest way to get rid of that is to put it in a container in the refrigerator. The fat will solidify leaving the water behind to drain. The liquid fat can sometimes be hard to draw through filter paper. You may want to get yourself a cheap vacuum filter (has a hand vacuum pump, got mine on Amazon for not much money). I tried this with raw shea butter and it worked pretty well, chicken fat is less viscous, so should work really well.

Might work easiest if you rendered it, vacuum filtered it, then refrigerated it to remove the water?

After that, if you wanted it even more pure, you might try sparging it with air and an aquarium bubbler. That would get rid of some of the smoky/cooking smells.

[SUP]

Oh wow! So many steps. I should look into getting a hand  vacuum pump.

I am increasingly beginning to wonder whether it is worth testing chicken fat. I have not really heard of it being used anywhere on leather anyway.

 

[AEBL]

Oh man, they were a lot less expensive when I got them from Amazon. I think I paid $30 ... this one is like $60:
(hand vacuum filter)

https://www.amazon.com/United-Scientific-Supplies-FLTKIT-Filtering/dp/B01MT3QS0P?crid=1TRHLKR70TT2U&dib=eyJ2IjoiMSJ9.y75g-i8DTumsSHCkpkGX2aO0ipGxWqsM-gyGr31RAFNUcTTmWlEc4OZQu097F7rAMXQZAu9np7gtyxQs5Xq0q3Me6-A0dsXkWVOJZErhPLcHJ02HQLhmVMQ09Sawt1nFhwqSa4CR-2dt3fwxtswxpiJYWH_Q-x5aE_j-WzXlZVzF9nG9NSJx_haheoVHX5X2uXzqTj4EIWXFNVcsBYgJUITzF8i8BifoALyJGPf4F58.PgOwkYgqdbMpjyOIjfyaspmEAYcUE4cZA_cYQadHotQ&dib_tag=se&keywords=vacuum+filter+paper+funnel&qid=1752093413&sprefix=vacuum+filter+paper+funnel%2Caps%2C130&sr=8-6

[SUP]

That does it. I'll see if the chicken fat that I get is clean enough. If not, I'm dropping the idea of using it. 

Thank you for investigating that. I was searching on Amazon and all I found was filters for vacuums. 

 

Edited July 9 by SUP

[dikman]

I wonder where they got these things from in the olde days when they supposedly used chicken fat?