Dry cleaning has become a part of our lives and when you hear the word dry clean what might come to your mind first is a person using a washing machine, soap and water but you might have seen a few clothes and materials were it was written dry clean only but when you dipped them in water, or put them in a washing machine and they change their color or shrink.
From history, while regular soap and water does the job of cleaning cloths, dry cleaners used hand washed clothes with kerosene and petrol and these solvents got the cloths clean thanks to lack of polarity compared to water which is polar with two hydrogen atoms which are positively charged and one oxygen atom which is negatively charged. With the polarity of water, it is able to dissolve other polar substances like the salt in sweat and a whole lot of things that are polar but substances like grease and oil are non-polar substance with the entire molecule not being separated as wither positive or negative charge even when individual molecules have their own charges.
So if we are to look at the cleaning and dissolving of substances, polar water dissolves polar salt while non-polar substances like petrol or kerosene dissolves nonpolar oils. The cloths with non-polar stains require dry cleaning which isn't using water instead they use dry-cleaning solvents which are non-polar just like kerosene or petrol that was used in the past.
During the time that Kerosene and Petrol was used, a lot of clothes after washing ended up smelling like petrol and kerosene and the tubs were these cloths were being washed also had the tendency of exploding so dry cleaners in the early 20th century switched to Stoddard Solvents or paint thinner which is a mixture of carbon based liquids formed during the process of crude oil refining. Thinners are non-polar and work similarly to kerosene and petrol to remove stains from cloths.
Thinner was a good idea and was able to remove oil, grease and other non-polar stains in cloth but it still didn't smell good and was still flammable so in the mid 20th-century, Nonflammable Chlorinated Solvents was introduced. The solvents are made up of chlorine atoms with carbon backbones such as Tetrachloride, Trichloroethylene and Perchloroetylene (PERC). You might have heard about PERC because of its popularity among people in the dry cleaning services since the 1940s but even PERC isn't perfect as it requires special spotting and washing with specialized detergents to get it cleaned off completely.
PERC was doing fine until 1991 when talks of it being toxic to the environment and to human health was raised. Researchers did their jobs and found out that breathing it could affect the kidney causing kidney damage, liver damage and risk of cancer, while in the short term eye irritation, and dizziness. Since the 2020s we have been seeing different bans and phaseout of PERC in dry cleaning services but we still use them in a lot of countries and since we need to dry clean a lot of our cloths, better alternatives will need to be looked at.
For now, the alternatives we have are Butylal, High-Flashpoint hydrocarbons, and Liquid Carbon Dioxide but they all come with their ups and downs which includes not cleaning properly, flammability, among other things. But for now, you can still enjoy your cloths being washed and cleaned with the good old fashion professional wet cleaning although it still has its downside and we are still on the search for the best cleaning method for our cloths.
Read More
- https://www.sciencedirect.com/science/article/abs/pii/S0301479716305151
- https://pmc.ncbi.nlm.nih.gov/articles/PMC7880597/
- https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2021.638082/full
- https://gaftp.epa.gov/ap42/ch04/s01/final/c04s021_1995.PDF
- https://www.sciencedirect.com/topics/chemistry/dry-cleaning
- https://www.tandfonline.com/doi/pdf/10.1080/10473289.2007.10465320?needAccess=true
- https://www.epa.gov/sites/default/files/2016-09/documents/tetrachloroethylene.pdf
- https://wwwn.cdc.gov/TSP/PHS/PHS.aspx?phsid=414&toxid=73
- https://manoa.hawaii.edu/exploringourfluidearth
- https://www.epa.gov/archive/epapages/newsroom_archive
- https://www.pca.state.mn.us/pollutants-and-contaminants/perchloroethylene-tetrachloroethylene-pce-or-perc
- https://venus-goa.com/ethoxylated-alcohol.php
- https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC5511734&blobtype=pdf
- https://www.tandfonline.com/doi/abs/10.1080/15459624.2016.1177648
- https://www.sciencedirect.com/science/article/abs/pii/S0896844602002668
- https://www.osha.gov/sites/default/files/publications/osha3253.pdf
- https://www.sciencedirect.com/science/article/abs/pii/S092696140180037X
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STOPWell, the improvement are remarkable, and I guess we keep making do with what we have until a better alternative comes up .