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Protect Against Gelcoat Blisters with the Interlux InterProtect® System

Prevention is always better than cure and it makes perfect sense to protect a new boat as well as an older craft. To achieve this protection, it's necessary to seal the hull surface by sheathing it with a water barrier over the existing gelcoat. Ideally, the best time to apply an anti-osmosis system is before launching the boat. Some boat builders now offer Interlux's InterProtect treatment as part of their production process, so it's 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.

Choose an InterProtect® System For Your Application: InterProtect® 2000E or InterProtect® HS

InterProtect 2000E and InterProtect HS are the industry standards for gelcoat repair systems, so your choice for the right product for your application depends on a number of factors, including your application procedures, VOC restrictions, and drying times. The tables below list the characteristics of both systems, as well as their recommended overcoat intervals.

Characteristics InterProtect® 2000E InterProtect® HS
Color Gray 2000E and White 2002E Gray
Application Methods Roll, brush, or spray Airless spray, brush, and roll
VOC 464 g/l 289 g/l
Volume Solids 45% 66%
Application Temperature 40-95°F (5-35°C) 41-95°F (5-35°C)
Theoretical Coverage 240 ft2/gal/coat brush or roll applied 151 ft2/gal to reach a DFT of 7 mils
Mixing Ratio 3:1 2:1
Solvent Interlux 2316N or Interlux 2333N Interlux 2316N or Interlux 2333N
Clean-Up Interlux 2316N Interlux 2316N
Pot Life 5 hours 2.5 hours

Recommended Overcoating Intervals:
InterProtect® 2000E

Minimum Maximum Minimum Maximum
41°F (5°C) 10 Hours 6 Months 10 Hours**** 24 Hours****
50°F (10°C) 5 Hours 6 Months 5 Hours 9 Hours
73°F (23°C) 3 Hours 6 Months 3 Hours 7 Hours
95°F (35°C) 2 Hours 6 Months 1 Hour 5 Hours
Number of Coats

*It usually takes 4-5 coats of InterProtect 2000E/2001E but the final film thickness of 10 mils DFT 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 DFT.

***Overcoating times will vary due to wide variations in temperature and humidity. The best method to determine when the InterProtect 2000E is Ready-to-Overcoat is to check the paint film using the "Thumb Print" test. If the InterProtect 2000E feels tacky and you can leave a thumbprint in the paint film without getting any paint on your thumb, it is ready for overcoating.

Test the paint film 1 hour after starting the application. Continue testing every 15 minutes using the "Thumb Print" test until reaching the ready-to-overcoat stage. Immediately begin to apply the Interlux antifouling paint once the primer has reached the ready-to-overcoat stage. Do not use this method with Epiglass Epoxy or InterProtect® 3000. These times do not apply to VC Offshore or Baltoplate, Micron® Optima or Fiberglass Bottomkote® Aqua. Do not use the "Thumb Print" test when applying VC® Offshore, Baltoplate, VC® 17m Extra or any vinyl antifouling over InterProtect.

****Only Micron® 66, Micron® CF, Pacifica® Plus, Trilux® 33 and VC® 17m Extra may be applied at temperatures below 50°F.

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

8 a.m. Give the boat a final sanding and wipe down.
9 a.m. Apply the first coat of InterProtect 2000E.
12 noon Apply the second coat of InterProtect 2000E.
3 p.m. Apply the third coat of InterProtect 2000E.

DAY TWO — Up to 6 months is allowed between coats of InterProtect 2000E.
8 a.m. Apply the fourth coat of InterProtect 2000E.
12 noon Apply the fifth coat of InterProtect 2000E (if needed).
4 p.m. Apply the first coat of Interlux® antifouling paint.

It usually takes 4-5 coats to apply the proper amount of InterProtect® 2000E/2001E, but the amount of paint is more important than the number of coats. Refer to Page 8 of the InterProtect® Product Information Brochure to determine the amount of InterProtect 2000E needed.

Substrate Temp

Touch Dry

Hard Dry

Pot Life

Overcoating Intervals Between Coats of InterProtect HS

Minumum / Maximum
41/5 7 16 2.5
7 hours / 3 months
60/15 4.5 8 2
5 hours / 3 months
73/23 3 6 1
3 hours / 3 months
95/35 1.75 3 50 minutes
2 hours / 3 months
IMPORTANT: The "Thumb Print" test cannot be used to determine when InterProtect HS is ready to overcoat. Refer to the InterProtect® HS Product Data Sheet for more information on applying antifouling paint to InterProtect HS. Apply enough InterProtect HS to reach 10 mils WFT (Wet Film Thickness), 7 mils DFT (Dry Film Thickness) for areas below the waterline, or a WFT of 8 mils and a DFT of 5 mils for above-water areas. This may take 3 coats by brush/roller, depending on the type of roller used, OR 1 coat by spraying, but the amount of paint is more important than the number of coats. To determine how much InterProtect HS is needed, refer to Page 8 of the InterProtect® Product Information Brochure.

Bottom                          Antifouling
     Blister Repair & Prevention

Interlux Antifouling Basics
How Antifouling Paint Works
Interlux Antifoulant Selection Guide
Painting Bare Fiberglass Bottoms
Antifouling Paint Systems for Various Substrates
Handy Specifications
How To Paint Previously Painted Bottoms
Interlux Applying Antifouling Advice
Antifouling Paint Calculator
Antifoulant on Aluminum Hulls
Interlux Antifoulant on Metal Outdrives, Keels and Centerboards
Hints for the Perfect Bottom Finish
Interlux Antifoulant FAQ
What is Osmosis Gelcoat Blistering
How to Recognize and Treat Osmosis Gelcoat Blisters
Protect Against Gelcoat Blisters with Interlux Interprotect
Interlux Gelcoat Blister Repair FAQ

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