Mold in Laminate sails

Problem: Mold in Laminate sails

Mold in Laminate sails can spread out in different ways. The beginning is always the molds spores. These can enter the sails different components or even be there already.

How mildew gets it's food

Easy access is found through injured parts of the sails segments. Kown are the perforations caused by stitchings and the edges of the sailcloth pannels. On the pannel edges, water can be pulled into the yarns by capillaric effect. This way it can penetrate up to 10 cm deep into the laminate. With the water mildew spores are transported to the inner. Another way into the laminate is unproof surfaces of the sail. Should your sail take water in the surface, you should react quickly, than the spores get plenty of food to grow fast.

Spores will start growing when two factors are given: food & humidity. Factors 3,4 & 5 as per below are beneficial for fast growth.

  1. Food: from inside the sail or furnished from outside
  2. Humidity: supplied from outside
  3. Oxygene: from surrounding
  4. Right temperature: from surrounding
  5. Right ph-value: alkaline supports growth, acidic slows growth

Of above factors, only the humidity access can be influenced on a sails tafetta (outside layer of sailcloth). Water is at the same time transport media for food, like dirt and bakteria and necessary elixir for life of the spores and later for the mold growing from those spores.

Should the laminate be glued together with the help of polyester glues, what is mostly the case, the mildew can feed also from the esther compound in the Polyester. This is known already for a long time, within polyester based construction materails for house building.

Should food or water not be available, the mold will fall into a kind of state similar to hibernation and stops growing. This is the way growth can be slowed down in a laminated sail.

Mold can take any colour. The colour it shows depends strongly on the kind of food it finds. It’s the karposoma, the “fruit” or body of the mold, that we can see when it reaches a certain visible size.

What does mold look like?


Strongly simplyfied, it has 3 components:

  • (1) the seeds: the spores, not visible (app. 1/11.000 of a mm)
  • (2) the karposoma, the later visible “fruit”
  • (3) the roots: the mycelium, invisible & not tracable

How do we treat mold infected laminates? What can be done?

First you have to differentiate between

  • mold on the outside of the sail
  • mold within the laminate construction of the sail

Second the intensity of the mold infection is important. Mold inside the laminate construction, cannot be treated! We cannot access the inner of a laminate construction. Mold on the outside of a laminate sail can generally be removed. With very strong infections and a few seldom kinds of mold, it can also be critical to remove it from the outside.

In early stades of mold infections, it is mostly possible to treat a laminate sail succesfully and free it from the karposoma. Evt. mycelia, the roots can not be removed and also not even determined.

This means, you can never grant 100 % success at such a treatment. Still all our tests show that on a treated sails, with an newly installed finish, molds come back only very slow and difficult: see here on an 8 year old set of Spectra sails, click here

 What is the conclusion we draw from this complexity of the subject?

Mold can be worst case already into a new laminate in form of spores. Should this be the case and a mycelium has been developped, there is almost no escape from mold anymore.

Our conclusion is that a laminate sail should always be well protected against humdity. It probably means that a laminate should be well proofed from day 1 after it’s construction. After being taken into use, the laminate should be regularly controlled on the functionality of the finish: should it take water, it has to be reproofed.

Most important is to keep the sail always dry! A difficult undertaking on board of a ship. Especially if it concerns furling sails, that are kept outside day and night without anymore protection than a UV-stroke. This does not keep away humidity and dirts, just UV-light!