This is a basic guide intended to convey the key points for refinishing old Gelcoat on fiberglass boats, RVs, and architectural plastics. This process can yield a very fine finish without the need for the spray equipment, or the safety and environmental conditions required for spraying. This method can be utilized by an amateur painter who is willing to prepare carefully and to practice a little to develop their technique prior to tackling the primary objective.
STEP 1. DEWAX THE SURFACE
For old Gelcoat Dewax and clean surface prior to sanding with a water based cleaner or a solvent. This very important step must be done prior to sanding. Sanding first will drive the wax into the sanding scratches. Water Based Cleaner: Use LBI 361 Verikleen or MaryKate MKT35 On/Off Cleaner. Be sure to scrub with an abrasive pad (LBI UA77477) and rinse thorough with water making sure that the rinse water “sheets off” the surface and doesn’t “bead up” as it does on a waxed surface. Solvent Cleaner: Use LBI 1271 Epoxy Solvent, LBI PL 48-16 Lacquer Thinner or LBI 1272 Denatured Alcohol Have plenty of rags and use the first rag to scrub the surface and soften the wax and then a clean rag to remove it before the solvent evaporates.
STEP 2. SANDING
For Gelcoat in fair condition (not heavily damaged, just generally dull and faded) sand with 320 grit paper to completely sand the entire surface and remove all gloss. More coarse paper may open porosity (pinholes) in the old Gelcoat which will require more work to fill them.
For rougher surfaces sand with 80 to 120 grit then fill and fair as necessary with LBI 340 or 940 Fairing Compound or LBI 395 Glazing Putty for very small scratches and pinholes.
STEP 3. PRIMING
You may want to apply Duratec primer to fair or coarse sanded surfaces as it will fill a lot of small imperfections and is very easy to sand. If the surface is pretty good and without the occasional deep sanding scratch apply the primer recommended by the manufacturer. This is a good time to practice you’re roll and tip technique. Evenly roll on the primer in the horizontal direction and follow by tipping or brushing in the vertical direction. A team effort with two people is helpful.
STEP 4. FINAL SANDING
Completely sand the surface to at least 220grit (320 grit is better) use your finger tips to feel for imperfection as you sand. Touch is often better than sight. When sanding is completed clean off the sanding dust and gently remove the last dust particles with a tack cloth.
STEP 5. TOPCOAT APPLICATION
Mask as necessary and make sure the area is clean and dust free. The temperature of the area and surface to be painted should be 60 degrees F or above. The optimum temperature is 70 to 78 degrees F. If you have prepared a practice surface now is the time to perfect your technique. Use LBI WOR730-9 TIZ Roller and LBI RED12053 Onyx Brush. Try rolling just the right amount of paint in the horizontal direction followed by tipping with a brush in the vertical direction to smooth it out. Too much paint will yield sags and runs. Too little will not yield a smooth glossy finish. This “Dress Rehearsal” will save you a lot of time and money not to mention a lot of sanding.
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