>>> I am surprised that you recommended the product have a 3 - 5 pH range.
When leather is read with a leather pH meter in the tannery it will reveal the pH value on a dry surface. It is mainly depending on the tanning agents, auxiliary including bactericide, fungicide, dyestuff and fatliquor as part of the leather constituents. Thus in most cases the Vegetable-Tanned leathers usually takes on a lower pH value that is why it is more pH sensitive. Another fact to know about leather is that the leather protein leather is an “amphoteric” material and any solution that is higher than the range of pH 3 – 5 will cause a shift of the ionic positive (+ve) leather protein fiber to weakens and shift to ionic negative (-ve). Remember that the leather constituents like the fatliquor and the others are ionic negative (-ve) charged. Ionic attraction behaves similarly like magnets with “like poles repels” and “unlike poles attracts”.
>>> I had previously thought that aiming for a neutral 7 pH was preferable.
pH is calculated by the power of 10. When a pH value of 7 is applied onto the leather, which has an average of 4. It will have a 3 points difference in ionic strength to the negative (-ve) for the protein fiber, while the other leather constituents are “non-amphoteric” will remain ionic negative (-ve) The 3 point difference calculate to the power of 10 becomes 1000 times off balance to the ionic negative (-ve) as well. Now can you see the damages slowly taken place as the ionic attraction weakens? Leather is pH sensitive as water is temperature sensitive and changes from ice, water to steam in the temperature range. Leather behaves similarly when put through the pH range it either strengthen the leather or weakens it denaturing to raw hide.
>>> Do fatliquors have the potential to cause the leather to go rancid if too much is applied?
The scent of the leather is much dependent on the quality of the fatliquor (ionic charged fat and oil), it should please any leather lover. Any awful smelly suppose “fatliquor” should not be used, so take a sniff of the bottle before you apply. Fatliquor is an emulsion same as fresh milk mainly with similar composition of fat, oil and water. In Fatliquor-5.0 it has 16.66% of ionic negative (-ve) charged fat and oil molecule encased in 83.33% of water content. With this composition as 83.33% of the content will evaporate that leave the breather pores open, it is unlikely to apply too much. When the leather is fully saturated with fat and oil it becomes less absorbent and you would know that it has reached it optimum level. An analogy is a wooden boat when put in water will soak up as much water as it can hold without allowing the water to come through. So a fully fatliquored leather will also resist the ingress of any unwanted water staining content especially from body oil, grease and sweat with constant body contact. Among the three content this unknown "sweat" is the worst culprit that eventually cracks the leather. You may want to know why then natural body oil, grease and sweat do damages to the leather as compared to your initial "Animal Oils and Petroleum Derivatives" as treatment?
Leather Approximate Quantity or Percentage of Fatliquor:
The quantities of fatliquor (fat and oil) contents retained in the leather after an universal tannery fatliquoring process may varies up from 14% to 16% depending on the leather types and it usage. This percentage drops as the fat and oil content diminishes or leaches through ageing, water, heat or chemical overexposure.
Leather rejuvenating or fatliquor replenishing is base on weight of the leather in relation to the percentage of remaining fatliquor. A simple calculation of percentage of fatliquor topping up requirement would be as follows:
If the weight of the leather in question is 100gm and fatliquor (fat and oil) content meter reading is less than 1%.
By applying 80gm of Fatliquor-5.0 to it will deliver an end result incremental of 13.3% fatliquor when dry as the 66.6% water contents evaporates.
In the leather rejuvenating Hydrator-3.3 > Fatliquor-5.0 > Hydrator-3.3 system, Hydrator-3.3 plays an important role by relaxing, opening up the inter-fibrillary spaces, facilitating and redistributing colloidal water movement, protonating and doing all the pre-conditioning work prior to fatliquoring including cleaning up any excess surface remnants to have a sticky-free surface. In practice with severe dryness the ratio for Hydrator-3.3 is 2 to 1 of Fatliquor-5.0.
It works out to be approximately 160gm of Hydrator-3.3 plus 80gm of Fatliquor-5.0 to replenish a 100gm dry leather from less than 1% back to the original tannery up from 14% to 16% fatliquor content.
In every bottle of Fatliquor-5.0 by weight content is comprises of 16.66% ionic negative (-ve) charged fat and oil, and 83.33% of water, the water content that encased the fat and oil molecule in an emulsion suspension when hydrogen bond with the ionic positive (+ve) leather protein fiber will break free and discharged from the leather structure to the surface.
>>> You have convinced me that fatliqours make sense, but then may I go further and ask you which product out there would be a good one to purchase and use?
You will need a Hydrator-3.3 > Fatliquor-5.0 Hydrator-3.3 combination system to work on fabricated leathers by non-emersion or emersion method.
Non-emersion application for obvious reasons
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Emersion application where it applies:
The fat and oil content will be hydrogen bond [positive (+ve) and negative (-ve) ionic charged] with the leather protein fiber in the dwelling process leaving behind the discharged or exhausted water content clear in an enclosed condition for observation with the same principle as electroplating process.
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Roger Koh
Leather Care System Formulator
Consultant / Practitioner / Instructor / Founder
web: www.leatherdoctor.com
forum: www.leathercleaningrestorationforum.com
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