WATER: Monday morning bleaching and post-vacation blues

When Joy Boutrup and I were teaching at Penland earlier in the summer she told the story of “Monday morning bleaching”. In old European laundries there was a serious problem with an increased number of holes left in fabrics that were laundered on Monday mornings. During the rest of the week the problem was lessened.


The issue turned out to be iron pipes. Water that had been sitting in the pipes all weekend leached ferrous out of the metal pipes. When ferrous is combined with bleach, the fabric will be compromised, resulting in holes. Once enough water had flowed through the pipes the amount of ferrous was decreased and there was no problem the rest of the week.

I have just experienced a related phenomenon in my own dye studio. After being away from home and studio a week or more, I observed that the water coming out of the studio tap was dark in color. Did this have to do with our shallow well? Was there contamination?

I suspected iron and tested the water for ferrous by stirring a very small amount of gall nut tannin into the water. When ferrous and tannin combine, the water will turn black. This is the principle of gall nut ink, which is made from iron + gall.

A small amount of gall nut tannin was added to both cold and hot water

Water from the studio cold tap was fine. There was no reaction whatsoever. But the hot water turned black immediately, indicating that there was likely a problem with my “on demand” hot water heater. A call to the plumber confirmed that after 10 years of use the heating element had likely deteriorated and the water was leaching iron from the housing of the tank.


I continued to observe the water. After running the tap regularly for two days the iron content was much less but still too dark to be acceptable for dyeing.

After 5 days the hot water seemed to be almost completely clear of ferrous – but not quite.


This was not a good situation for a dye studio and I was forced to use only water from the cold tap for all processes. Yesterday I had a new water heater installed. All water is now completely free of ferrous!

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Soft acidic water is far more likely to dissolve iron in pipes or other sources. Hard, alkaline water won’t present as much of a problem. My mountain well water is very soft and close to pH 6, which is slightly acidic – the perfect water to leach any metal available. It’s a reminder that all dyeing begins with the water. Some mysteries in the dye studio can be solved by simply looking at the water.