As a result, I contacted the Head of Conservation at the Leather Conservation Centre in Northampton for further clarification of the points she had raised in her article.
This is a copy of her reply:-
Thank you for your email and I am pleased that you found the article informative.
There is, as you say, a lot of confusion regarding “feeding” leather. One of the big problems is that generally manufacturers and suppliers of such dressings are always keen to tell customers to use it and use it regularly with no regard as to the leather.
My standard “rant” is as follows -
“Generally we do not recommend using leather dressings because we find that, apart from being irreversible, they can cause damage to the leather. This is particularly the case if too much is used or used too often. The long term effects of over-oiling leather are that oils and fats can encourage bio-deterioration, spue (white residue on the leather), oxidise and stiffen the leather, discolour (ie darken) and stain, leave a sticky surface and wick onto nearby material, soften the original finishes and decoration, attract dust and impede future conservation treatments. It can also lead to splits in the leather where the fibres slide apart. The solvents in dressings can also affect surface finishes. So, dressings have lots of potentially disastrous side effects.
You have to be sure that the object needs it before applying a dressing and it must be applied very sparingly.”
To give you a little more information –
I do not know what sort of leather is used in modern Morgan cars but most leather (well over 90%) manufactured nowadays is chrome tanned leather which is very different to the historic, vegetable tanned leathers which is what we mostly deal with. Our knowledge and expertise is on historic leathers so I really cannot comment on the leather in your Morgan, unless you know that traditional leather and finish have been used.
Most dressings are not designed for the leather but rather are really designed to soften the plasticizers in the finishes to prevent hardening and cracking. They do not even penetrate into the leather at all. However, when the finish is degrading, starting to rub off, or with historic leathers that had little or no finish then the dressings get into the leather fibres and start to damage the leather.
Every piece of leather is different and this is particularly the case with older leathers so there is no one answer fits all when it comes to conserving leather.
Historic vegetable tanned leathers are much firmer than new leathers and because owners do not realise this they often start added dressings to try to soften the leather, which was never manufactured to be soft. Because of this they repeatedly apply dressings to make the leather feel softer and to make it supple not realising that they are actually storing up trouble.
Another reason that people seem to add dressings is because they think they leather is dry – and this may be true but dry means lack of moisture not lack of fat. Leather really likes a stable atmosphere with a humidity of around 50%RH and if consistently kept in dry atmospheres the leather can begin to feel stiffer and will shrink but it is humidity not fat which is required to replace the lost moisture. Leather can also dry out and crack after it becomes very wet (perhaps an open car which goes out in the rain) and is then dried (this is particularly noticeable if it happens repeatedly). I have noticed that some modern cleaners recommend “rinsing thoroughly” which we would not recommend.
For any historic cars (certainly pre 1950s) I would recommend that qualified/experienced leather conservators are engaged to carry out conservation treatments because it is so easy to cause damage.
For newer cars then it may be wise to ensure that any products applied to the leather are suitable for the finish on the leather (different solvents can damage different finishes) but always be cautious and sparing in any applications.
I think if you wish to pass on any nugget of information to your fellow owners then I would say “Leave it alone!”
Hope this helps
Yvette A Fletcher BA Hons, MA, ACR
Head of Conservation