The further effects of climate change
22 January 2024With the exception of the climate change deniers I think most of us accept that the phenomenon has been with us for quite some time, and is now having a noticeable influence on our weather particularly during the winter period when, in the latter part of last year, serious flooding took place around the UK and elsewhere. While in some respects the change in our weather may be beneficial to our industry bringing in additional work from floods and the additional staining and soiling generated by the wet conditions generally, it also brings with it additional day to day risks during the gloomy wet days which at times have seemed never ending.
Relative humidity
Looking back to last year and the start of the wet weather, in October I took a close look at the humidity levels that prevailed day to day and was surprised to find that relative humidity (RH) - the amount of moisture in the air, often averaged around 93% throughout the wet periods and occasionally, for shorter periods approached 100%. In the York area in the north of England the average for the month of October was 86.6% with a high of 99%. Although prolonged RH levels of this order are of little consequence to wetcleaners they do present some serious risks for all drycleaners and particularly for those specialising in designer clothing; so I think now would be a good time to remind ourselves of the ongoing risks from very high atmospheric humidity.
Humidity and textiles
To varying degrees all textile fibres absorb moisture from the atmosphere and their capacity to absorb moisture is known as textile regain. Standard Textile Regain is calculated at 65% RH. However, textile regain increases in line with increasing atmospheric humidity and while it is common for humidity levels in winter to fluctuate at levels around 80%, for the drycleaner there are progressively increasing risks of shrinkage and particularly felting from sustained humidity levels of 80% RH and above. Although high prevailing levels of moisture in the atmosphere present shrinkage risks for other textiles, animal hair fibres (wool/animal hair regain at 65% RH is 16%) are by far the most at risk (see also February 2022 What Went Wrong). In particular high quality angora, cashmere, mohair, camel hair, alpaca and wool garments are at particularly high risk of felting in drycleaning from prolonged high atmospheric humidity levels well in excess of 80%.
Drycleaners should also bear in mind that during protracted periods of very high humidity (check your weather app) all fabrics are likely to be at well above their normal regains and the extra moisture they are carrying, particularly when combined with general pre-spotting soap/water mixtures, could give rise to excess moisture being introduced into the drycleaning machine. Cloudy or milky solvent is a good indicator that things are not what they should be.
Reducing the risk
Unfortunately, there is no practical method available to us for checking the moisture content of garments deposited for drycleaning. It is also the case that animal hair fibres can hold up to 28% moisture before they begin to feel noticeably damp (well above their normal regain of 16% at which they can safely be drycleaned). All animal hair textiles are at increasing risk of felting in drycleaning as their regain rises above 18% with angora, mohair and cashmere being very much at risk. Although it is not possible to check or even assess the regain/ moisture content of textiles, under normal weather conditions the risk of felting in the machine is low but when atmospheric humidity remains high, at risk items should be hung and allowed to condition for at least two hours in a warm dry area or hung in a drying cabinet if available, before being drycleaned - garments left in a vehicle overnight before dryclening are particularly at risk.
Top tip - to be on the safe side, before drycleaning, high value/designer/ very high risk animal hair items, it is a good idea to hang and condition them irrespective of the prevailing levels of relative humidity.
