Leather

Follow the guidelines
Cleaning leathers and suedes involves special processes which broadly follow the procedure described in British Standard 7269 part 2. This uses a two-bath process in perc, adding leather oil to the final bath to replace the tanner’s oils, which are inevitably lost in the solvent.

The cleaned leather is then tumbled (often with sponges) to improve its suppleness and re-sprayed. This restores the colour, surface texture and handle still further.

Some of the leather’s colour will have been lost in the solvent, so a suede would be sprayed with an oil-water emulsion to enhance this and produce an even result.

A grain leather might need to be re-finished with a surface coat of colour followed by one or more sealing layers. The final finish can be matt, semi-matt or gloss depending on the sealing coat used. Nubucks require a special finish to restore the fine surface texture and colour without damaging the nap.

These processes need special equipment and considerable skill, training and experience and so leather cleaning has to date been carried out by a specialist rather than a High Street cleaner. However, the introduction of milder solvents has changed this to some extent. Perc has a high solvency power (Kauri-butanol value of over 90) but hydrocarbon is much gentler at 30Kb and cyclosiloxane is even milder at 12Kb.

Perc will strip out all the tanner’s oils so re-spraying is essential, but hydrocarbon removes less of these oils and cyclosiloxane removes hardly any of the oils. So more cleaners are trying to clean leathers themselves rather than sub-contracting the work.

Case Studies

Explaining the label
Problem: A suede leather garment was labelled only with a leather-mark with an F and three stars (see picture). The cleaner processed it in hydrocarbon without adding any oil but this produced a faded and shrunken garment.

Cause: This garment has been care-labelled according to the British Standard for leather garments (BS7269 part 1). The leather mark indicates a leather cleaning process and not a textile one. The F means that it should be cleaned in hydrocarbon solvent. The three stars mean that the extractable oil content is 10% and it requires the final cleaning bath to be charged with 150g/litre of leather oil to replace the lost oil.

Responsibility; The cleaner is to blame for the result because he did not include enough oil in the final cleaning bath.

Rectification: The result can almost certainly be corrected by re-cleaning in a single-bath process with the right amount of oil in the bath. It will then need professional re-spraying with an oil and water emulsion.

Fur coat turns yellow
Fault: This coat was cleaned in cyclosiloxane but afterwards the pocket openings and cuffs looked distinctly yellow at the edges

Cause: The pattern of the yellowing points to contamination with skin oils as the main cause. These do not dissolve well in any drycleaning solvent and those that survive the solvent wash tend to yellow with the warmth of the drying air-stream.

Responsibility: The relevant standard, BS7269 part 2 defines the reference process for leather cleaning in perc. This requires an air-off-the-cage temperature of 45 – 55C, corresponding to an air-into-the-cage temperature of 65 – 75C. These temperatures are sufficient to cause yellowing of unremoved protein soiling, so the fact that the cleaner used cyclosiloxane is not relevant.

The responsibility lies with the wearer for soiling the garment and not with the cleaner for failing to remove it.

Rectification: The yellowing consists of oxidised protein from the skin oils, which is exceptionally difficult to remove without damaging the fur. The garment is best left. For the future, pale furs are best cleaned with the drying thermostat set to the lowest practical setting to reduce the risk of yellowing.

Leather turns stiff and crinkly
Fault: The drycleaner decided to process a suede-leather garment on-site in hydrocarbon but produced a stiff, crinkly result and an unacceptably shrunken garment.`

Cause: A professional tanner will strip the leather of all its oils and then re-oil it to give durable garment material.

The oils lubricate the fibrous leather matrix, giving the material its suppleness and elasticity. The solvency power of hydrocarbon is sufficiently low to produce little or no oil removal in many instances.

However, occasionally the power of the solvent is sufficient to strip out all the oil, leaving the material stiff and crinkly and often faded overall,.

Responsibility: The responsibility here lies with the cleaner. The reference process for leather cleaning given in British Standards involves re-oiling in two stages: charging the solvent in the final bath with oil and then evening out the final result with spray re-oiling as necessary.

Rectification: The garment should be re-cleaned with oil in the final cleaning bath, which will overcome much of the problem. It will probably then need re-spraying to even out the panel-to-panel variation, tumbling cold with sponges and then brushing on a mannequin to restore the nap.

Grain leather loses its sheen
Fault: A grain leather jacket lost its medium sheen finish after it had been cleaned in cyclosiloxane. Cause: Tests on the uncleaned belt revealed that the finish could not withstand any drycleaning solvent. Just a few seconds in cold solvent with mild mechanical action was sufficient to remove the sheen. This happened in tests with perc, hydrocarbon and cyclosiloxane.

Responsibility: The garment maker should be taking responsibility for the owner’s dissatisfaction here. Labelling a garment for professional (or specialist) leather cleaning is of no use if the finish cannot withstand any of the solvents used for leather cleaning.

Rectification: It is not possible to correct the fault. Re-spraying with a standard finish proved impossible, because the finish simply soaked into the porous leather surface. For the future, if the cleaner does not have spray equipment, then a simple fastness test is essential before attempting any grain leather.

Marked variations in colour
Fault: The panels in this garment varied greatly in colour after it had been drycleaned in hydrocarbon.

Cause: It is difficult to dye leather and obtain a completely colourfast result. The take-up will vary over the garment as some parts will be more open and absorbent than others. So colour loss during drycleaning will also vary, resulting in the panel-to-panel variation.

Responsibility: This is a natural feature of any hide, so although the tanner/dyer is responsible for the overall shade and colourfastness, they should not be blamed for subsequent variations, which are unavoidable. British standards allow the garment maker a colour change during drycleaning of 3/4 on the International Grey Scale – a much greater change than that acceptable for textiles.

Rectification: Small variations in colour can be disguised by re-oiling to a slightly higher level. Larger variations in grain leathers require spray re-colouring and spray re-finishing using a professional spray booth with air extraction and the appropriate safety precautions. For the future, simple colourfastness testing will indicate which leathers are most likely to suffer heavy colour loss and should therefore be sent to a specialist.