What is Osmosis?

The term “Osmosis” has been in common usage since the early 1970’s when the problem first came to light. It is now understood that the osmotic process is not the whole story and that a process known as “Hydrolysis” is also involved, perhaps to an even greater extent.

Whatever the scientific explanation behind “Osmosis”, there are several factors that have been found to increase the likelihood of it occurring:

  • Long periods afloat without the boat being removed for layup ashore
  • Warm tropical waters or warm inland waters are worse than cold waters
  • Fresh water is worse than salt water

By the time that blisters are visible on a hull, the process of osmosis is fairly well advanced and any superficial treatment of the blisters is likely to be a waste of time and effort. The only worthwhile remedy is to pay for a full professional osmosis treatment at a skilled and experienced boatyard.

Douglas Boatyard is an International Paints approved osmosis treatment centre and all boats treated carry a three year warranty.

Osmosis Treatment Quotations

Please be aware that not all osmosis treatment centres provide all-inclusive quotations and the final invoice can sometimes be very much more than was originally quoted. Douglas Marine Limited include for all boatyard fees, for cranage and boat handling charges, and for all storage fees for the duration of the work in their quotations for osmosis treatment. Please ask us for a competitive quotation.

Osmosis Treatment

The process of treating osmosis at Douglas Boatyard can be summarized as follows:

  1. The vessel arrives at the boatyard, either by water or by road.
  2. The boat is craned from road transport or slipped from the river.
  3. The hull skin fittings are removed where necessary.
  4. The existing gelcoat is removed using a proprietary gelcoat peeler.
  5. The peeled surface is then abraded using a disc sander.
  6. A hot-wash system is used regularly over a period of months to remove the styrene chemicals from the hull that originally caused the osmosis.
  7. When the styrene chemicals have been removed from the hull and the moisture content has been reduced to an acceptable level, one coat of solvent-free International Gelshield Plus is applied.
  8. Epoxy fillers are applied to rebuild and fair the hull surface.
  9. The surface is then sanded and faired.
  10. A further three coats of solvent-free Gelshield Plus epoxy are applied.
  11. One coat of Gelshield 200 is applied.
  12. One coat of hard antifouling paint is applied, then one coat of soft antifouling paint of a colour to the customer’s choice.
  13. Once the treatment has had sufficient time to cure, the boat will either be loaded onto road transport or launched to the river, as required by the customer.

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