[LTT Leathercare]

Chemical, Heat, Agitation, Time is explained in the IICRC S300 in relation to leather and fabric cleaning and is well worth your consideration if you are cleaning leather.

Leather on (domestic) furniture should be thought of in three states:

1.   That which has never been in contact or flexed (o/s backs and o/s arms)
2.   Leather that has been subject to flexing but not much contact (borders, extreme areas of arms and back cushion and maybe some parts of seats)
3.   Those areas that are subject to body contact (this should be divided into regular direct contact with skin and those less exposed)

Each area should be considered carefully and proposed cleaning subjected to CHAT analysis.

CHEMICALS: because finishes on leather are difficult to chemically analyse in situ it is best to keep this simple to restrict unexpected reactions.  This is why we stick to detergents formulated specifically for leather cleaning by producers with a good pedigree and labs to support testing etc.
 It does not take long to learn what sort of reaction to expect from them.  Anything unusual should stop you and make you reassess.  We have found that adverse effects created by tried and tested products are almost always a problem with the leather and not the product. Varying products, trying a bit of this and that will give you mixed reactions and inconsistent results.  Keeping products simple means you can gauge reactions and results more accurately.

HEAT: is a sector that cannot vary much in Leather Cleaning.  Warm water for cleaning does increase the effectiveness of chemicals, but you are limited in temperature by hand cleaning processes which are more controllable then machines for leather cleaning at present.

AGITATION; is an area with scope.  But it is limited by your assessment of the stability of the surface being cleaned and strangely the dirtier the surface the more carefully it should be cleaned (heavy soiling damages surfaces so they are likely to be more sensitive to strong chemicals and heavy agitation).  Do not confuse agitation with aggression.  Change the type of agitation for different situations by changing the source of agitation eg: a sponge is different from a cloth, is different from a soft brush, is different from a stiff brush.  Learning to clean leather is more about the type of agitation required to get the best performance out of your chemicals not the amount of power of chemicals or agitation.

TIME: is the other area that can be used to vary your cleaning approach to varying situations.  Time turns your cleaning product into a pre conditioner without having to complicate your chemical choice.  Letting your product dwell is a safer approach than increasing chemical strength or pressure of agitation (extra heat is not usually an option) both of which can create unexpectedly sudden adverse reactions.

The above look at CHAT is very brief and should be taken as a starting point.  The condition of the leather surface will dictate your results much more than anything else and using CHAT analysis should help you approach it in the safest way.
ŠLTT2007

[carpetguy]

Well constructed dialogue, which covers a fair bit of ground and is absolutely logical in it's content.

My only concern would be the advice to allow product, to dwell, as this could easily result in streaking, or non uniformity, in cleaning, which is more apparent in leather, than fabric.

When I use the Von Schrader machine it speeds up the process, by covering the back, sides, upright cushions much more quickly.

rob