P40_41

HOW TO RECOGNISE AND TREAT OSMOSIS

THE MAIN SYMPTOM, 'BLISTERS' – Blisters are the most common warning sign and if identified should be followed up with immediate professional examination. Blisters can vary from small pinhead blisters, to areas as large as the palm of a hand. The presence of any fluid behind a blister indicates a potential problem. If the fluid has a pungent, vinegary odour or feels greasy or sticky when rubbed between the thumb and forefinger, there is a high probability of osmosis. Before any treatment is carried out, you need to establish what has caused the problem. We recommend that you seek the advice of a professional surveyor.

Some blisters occur for reasons other than osmosis. They are often evident as a rash of small pinhead blisters or swellings, either locally (often around the water-line) or over the entire underwater area. These blisters are hard and difficult to break and when broken open will be dry, with no odour evident. The likely cause is air voids. This is not a serious problem, but hull moisture levels should be checked before commencement of any remedial treatment.

OTHER WARNING SIGNS TO LOOK FOR ARE –
STAR CRAZING – This effect can occur where the gelcoat is brittle. Fine cracks usually form due to severe flexing or impact damage, allowing water to seep into the laminate.
PINHOLES – Tiny bubbles present in the gelcoat reduce its effectiveness and promote rapid water absorption.
PROMINENT FIBERS – Seen protruding beneath or through the gelcoat and can cause ‘wicking’ where water is drawn into the hull by capillary action.
UNDERCURING OF THE GELCOAT – Incorrect mixing or application in unsuitable conditions can cause failure to cure properly. This results in porosity and may lead to water ingress.

	IMPORTANT STEPS IN THE REPAIR OF GELCOAT BLISTERS
1	PROPER PREPARATION OF THE GELCOAT This includes getting all of the antifouling paint off and removal of as much gelcoat as necessary to get the hull dry (i.e. the entire gelcoat or just small areas). A professional, who has looked at your boat, should make this determination.ouling.
2	DRYING OF THE HULL This is the most critical step in the process. If you do not get the hull dry it will re-blister. We recommend a comprehensive washing and drying procedure.
3	APPLICATION OF INTERPROTECT® 1000 or EPIGLASS® HT9000 RESIN This solventless epoxy seals up the laminate and fills any cloth that has been voided of resin. This should be done before using fillers to fill the voids.
4	APPLICATION OF INTERPROTECT® 2000E or INTERPROTECT® 3000 These epoxies are used as a water barrier to minimize the possibility of reoccurrence of damage.

Before starting a gelcoat prevention or repair system refer to the Interprotect® 900E System Guide before starting any work. Call I-800-468-7589 or send an E-mail to interprotect@yachtpaint.com to obtain a copy

HOW TO PROTECT AGAINST GELCOAT BLISTERING

Protection is always better than cure and it really does make sense to protect a new boat as well as an older craft. To achieve this protection it is necessary to sheath the hull with a water barrier to seal the surface. This is done over the existing gelcoat. There is no better time to apply an anti-osmosis system than when the boat has not yet been launched. Some boat builders now offer Interlux's Interprotect® treatment as part of their production process, so it is worth finding out if this is the case. However, it must be stressed that protective systems cannot stop osmosis once it has started, or prevent it from occurring in poorly constructed hulls. It is important that a full check is undertaken before starting.

RECOMMENDED OVERCOATING INTERVALS
TEMPERATURES	TIME BETWEEN COATS OF INTERPROTECT® 2000E**		FIRST COATING OF ANTIFOULING
TEMPERATURES	MINIMUM	MAXIMUM	MINIMUM	MAXIMUM
40°F (5°C)
50°F (10°C)
60°F (15°C)
77°F (25°C)
95°F (35°C)
NUMBER OF COATS*	4/5		1

*It usually takes 4–5 coats of Interprotect® 2000E/2001E but the final film thickness of 10 mils D.F.T. is more important than the number of coats.
**If you exceed the maximum dry times between coats of epoxy you must sand with 80 grit and apply at least one more coat of Interprotect® 2000E/2001E to ensure having 10 mils D.F.T.

KEY:

Hours

Weeks

Typical work schedule for application of Interprotect® 2000E at 70°F (21°C)

DAY ONE
8 a.m.	Give boat final sanding and wipe down
9 a.m.	Apply first coat of Interprotect® 2000E
12 noon	Apply second coat of Interprotect® 2000E
3 p.m.	Apply third coat of Interprotect® 2000E
DAY TWO – Up to 2 weeks is allowed between coats of Interprotect® 2000E
8 a.m.	Apply fourth coat of Interprotect® 2000E
12 noon	Apply fifth coat of Interprotect® 2000E (If needed*)
4 p.m.	Apply first coat of Interlux antifouling paint

It usually takes 4–5 coats to apply the proper amount of Interprotect® 2000E, but the amount of paint is more important than the number of coats.

Your best line of defence against gelcoat blistering

INTERPROTECT® 1000/1001	EPIGLASS® HT9000 RESIN	INTERPROTECT® 2000E/2001E	INTERPROTECT® 3000/3001	VC® TAR2	WATERTITE
• Solventless epoxies used to seal the laminate and cloth • Use where Gelcoat has been removed or breached		• Two-part epoxy water barrier with Micro-Plates® • For use in prevention of and repair of osmotic blistering	• V.O.C compliant two part epoxy water barrier with Micro- Plates®. • Can be used down to 32°F (0°C)	• Two-part epoxy water barrier for use with VC®17m or VC® 17m Extra, thin film antifouling paints	• Filler for repairing blisters and damage

	IF THE BOTTOM IS NEW OR UNPAINTED
1	Clean the surface thoroughly with Fiberglass Solvent Wash 202 or Fiberglass Surface Prep YMA601. uling.
2	Remove all traces of antifouling, using Interstrip 299E. Inspect the hull for signs of damage or cracking and repair any defects with Interprotect® 1000/1001 or Epiglass® HT9000 resin and fill with Watertite Epoxy Filler. In the event of more extensive damage being found, make sure that the water has not already entered the laminate.
3	Sand the gelcoat thoroughly using 80-grit sandpaper, then remove the sanding residue using Fiberglass Solvent Wash 202.
4	Mix three parts Interprotect® 2000E base to one part Interprotect® 2001E curing agent, by volume. Mix only what can be used in four to five hours. Apply coats of Interprotect® 2000E/2001E following the overcoating intervals in the chart below. Apply enough Interprotect® 2000E/2001E build a 10 mil Dry Film Thickness (D.F.T.) This usually takes 4-5 coats but the final film thickness is more important than the number of coats.
5	Apply Interlux antifouling paint following the overcoating intervals listed above.

IF THE BOTTOM HAS BEEN PREVIOUSLY PAINTED, COMMENCE WITH STEP 2.

How much Interprotect® 2000E/2001E do I need?

It is the best to actually measure the wetted surface area of the hull. If this is difficult to do, a close approximation can be made by multiplying the length overall, times the beam, times 85%(L.O.A. x Beam x .85 = wetted surface area). Divide the wetted surface area by 60 for brush and roller applications and by 45 for spray application. The resulting number is the number of gallons that need to be applied to reach a 10 mil dry film thickness.