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

[SUP]

The 2nd part of the experiment:

This has leather pieces soaked in one of the following:

Lanolin

Tallow

Cod liver oil

Mixture of mineral oil and coconut oil

Smoothness: In this set, the pieces treated with the oils, whether cod liver oil or the MO-CO mix, for the most part, are smoother and softer than the ones treated with Lanolin or tallow, although only marginally so. But it is seen across all the locations.  However, in spite of being smoother, they feel a little more dry than the leather treated with  Lanolin or Tallow.

Shape: The lanolin treated leather maintained its shape the most across locations, closely followed by tallow. The leather treated with the oils showed a small amount of warping. This is a slight change, but it is present in the leather in all locations.

Stiffness: The leathers treated with tallow and lanolin showed a slightly greater degree of stiffness than the ones treated with oils. The cod liver oil produced slightly more stiffness than the MO+CO  which produced barely any stiffness at all.

Smell: None of the products used maintained their smell. The smell of lanolin, tallow, cod liver oil and coconut oil are completely absent in all the leather pieces, across the board.

 

The pieces kept outside showed significantly mor darkening, drying and stiffness than any other pieces.

The darkening was very similar across all treatments, being marginally more in the CO+MO treated piece. The dryness was similar across treatments as well, as was change in shape  but Lanolin did not cause any change in shape at this point. All the treatments produced slight stiffness except for the MO-CO mix. That piece of leather is still soft and pliable.

The smells of the Lanolin, Tallow, Cod liver oil and Coconut oil are completely absent in all the pieces.

 

The following information is mainly about the leather pieces kept in locations other than outside:

The leather pieces treated with Lanolin have maintained their flat shape across locations. They are less dry than the oil treated leathers although they do not feel as smooth. The difference is slight but present in all locations. They are also slightly more stiff than the oil treated leathers, although less than the Tallow treated ones.

Tallow has made the leather pieces stiffer than any of the other products. The pieces have darkened slightly as well and are the stiffest of all the pieces in the different locations. They have maintained their shape for the most part, except in the outdoors sample.

Cod liver oil has darkened all the pieces slightly and uniformly in all locations, significantly more in the outdoors sample. The pieces are all holding their shapes reasonably well although less than any of the pieces treated with Lanolin Tallow or the MO+CO mix. The pieces are also slightly dry and slightly stiff.

MO+CO: These pieces darkened slightly and show some extent of dryness, the extent depending on the location, but they remain soft and pliable and are holding their shapes reasonably well. The dryness and color change is comparable to cod liver oil but the latter pieces show a slight change in shape in all the locations that is much less in the CO+MO.

 

Mineral oil and Petroleum Jelly for water resistance - a short report this time.

My 2nd leather piece treated with petroleum Jelly (PJ)+Mineral oi (MO) seems to have disappeared as well.

All the pieces remained outside, in the heat initially, then rain and freezing temperatures.

They are all, pliable and reasonably soft. They are all also very dark, the MO and the MO+PJ treated ones more than the PJ treated ones.

I kept a drop of water on each of the pieces and waited.

The Control absorbed the water at once.

The MO treated one absorbed the water in about 2 minutes.

The leather piece treated with MO+PJ has the water droplet unabsorbed 10 minutes later, but the edges may be slightly fuzzy.

The water droplets on the leathers treated with only PJ seem to show the greatest water resistance- the water is completely unabsorbed, edges clear.

A half hour later, astonishingly, the water drops on the PJ treated ones are getting gradually absorbed and are flat now but the droplet on the PJ+MO one, is still virtually unabsorbed.

So clearly, PJ provides good water resistance on leather. When put together with MO, it might work better. However, since I have only one sample for this, I will need to test this on more samples.

But it is promising.

Edited January 31 by SUP
Missed adding 2nd photograph.

[fredk]

[fredk]

We have now done 16 months of testing. (October '23 to end of January '25)

All the pieces are much the same as on June 6th 2024, with only some slight changes on a few pieces

Set #1, the Car set

1. Baby Oil; Both sides are dark, slightly lighter on the reverse side, More flexible than Control 1 (C1), No smell,  No sign of rot or fungus

2. Cooking Oil (rape seed);   Both sides very dark, Slightly more flexible than C1, Stronger cooking oil smell, No sign of rot or fungus

3. Lard (pork fats);  Light but darker than C2, Flex is about the same as C1,  No smell, No sign of rot or fungus

4.  NFO Compound; Both sides very dark,  Flex is better than C1, No smell, No sign of rot or fungus

5. Olive Oil ( Pure Extra Virgin); Both sides very dark, Flex is only slightly better than C1, Smell of cooking oil is stronger, No sign of rot or fungus

6. '3 in 1' oil (benzine); Both sides very dark, slightly lighter on reverse side, Flex is much stiffer than C1, Slight noticeable smell of '3 in 1' oil, No sign of rot or fungus

7. Vaseline; Colour is almost back to the same as C1, Flex is stiffer, No smell, No sign of rot or fungus

 

Set #2 were hung outside on a wood frame. They got light and heavy rain with periods of sunshine,  warm overcast and wind, both light breezes and strong winds

The same oils were used in the same sequence . Control C1A was hung with the other pieces

All have been lost except;

4.  NFO Compound;  Both sides are medium dark, Flex is better than C1A, No smell, No sign of rot or fungus

In conclusion; So far there has been no rot, no fungus and most importantly NONE of the oils or fats, especially the cooking oils/fats, have gone rancid

When I have time, maybe next week, I'll start a new batch for hanging outside 

Edited February 12 by fredk

[SUP]

Nice! 

I have to make a couple of new ones too.

[YanaG]

Just wanted to say thank you for doing this experiment, information on the mineral oil is indeed very valuable!

[SUP]

1 hour ago, YanaG said:

Just wanted to say thank you for doing this experiment, information on the mineral oil is indeed very valuable!

I'm glad you found the information useful, @YanaG. Welcome into the forum.

[YanaG]

1 hour ago, SUP said:

I'm glad you found the information useful, @YanaG. Welcome into the forum.

Thank you) A lot, if not most of leather treatments sold in my country are mineral oil based, I doubt you could even get pure neatsfoot oil at all, so the topic is very helpful!

[SUP]

2 hours ago, YanaG said:

A lot, if not most of leather treatments sold in my country are mineral oil based,

Oh. I didn't know that. And your leathers are fine, are they not? With the mineral oil based treatments? 

[fredk]

On 2/12/2025 at 2:13 AM, fredk said:

. . .

Set #2 were hung outside on a wood frame. They got light and heavy rain with periods of sunshine,  warm overcast and wind, both light breezes and strong winds

The same oils were used in the same sequence . Control C1A was hung with the other pieces

All have been lost except;

4.  NFO Compound;  Both sides are medium dark, Flex is better than C1A, No smell, No sign of rot or fungus

. . .

I've found set #2. They were in a box inside the car

I'll get them sorted out, re-oiled and re-hung outside asap

I'm thinking of ending this on the 2 year anniversary. Other than darkening and some change in the leather temper nothing is happening. No rot, or nuffin. If it hasn't happened in 2 years I doubt it'll happen in 3, or 4 . . . . 

[SUP]

I'm glad you found  the set.

I've added my missing control piece.

At this point, after Sept 2025, I plan to report once a year or so. A couple of hours to report once a year I think I can do.

It appears, does it not, all in all, that leather in general is pretty forgiving of whichever oil we use, as long a we do use some oil to lubricate it? I like the mineral oil because there is absolutely no chance of rancidity no matter how much one uses.

I realized that is significant because someone I know 'stuffed' her veg tanned leather bag (t make it 'healthy', don't ask) with first olive oil, then I know-not-what because she brought it to me stinking of rancidity. Not neetsfoot or mink or coconut because the former two do not turn rancid and smelly and the latter, I recognize the smell of rancid coconut oil and this is not it. I cannot get it clean - I actually, in desperation, washed and scrubbed  it with soap and water and hung it to dry, twice, with not the slightest effect. The leather is not damaged in spite of that rough treatment. Just a little dry to the feel but the smell remains! Not cracked or warped either.  used cold water and hung it to dry int he cold. 

Planning to use Limonene on it this week end. It is ruined anyway, she cannot use it, might as well experiment.

Keeping my fingers crossed.