Reprinted from April Issue, 1999


Fiberglass Hull Restorers:  21 Month Report

Of the DIY products tested, PoliGlow, New Glass, and Vertglas show the most gloss and last longest. Professionally applied Microshield is even better, but costs more.

Remember when your boat was new? Chances are that if you've had it for more than a few years, the once-shiny gelcoat has become dull and, if it were a color other than white, faded and a bit blotchy looking. The past few years have seen a proliferation of products designed to bring back the new, glossy look to weathered topsides. These "hull restorers" are typically more durable than waxes though less durable than a high-quality paint. Most of these products are also less expensive and easier to apply than paint.

We've been conducting tests on eight such products (we originally had a ninth, but it has been discontinued) for the past two years, with more than 21 months of actual exposure to the elements. We looked at them after a year of exposure (PS, July 1, 1998 and PER, May 1998), re-applied the restorers--they don't claim to last for more than a year or so with a single application--and put them back out to weather. To reiterate what we've said previously, these products are best thought of as temporary fixes. All of them can dramatically improve the appearance of a weathered fiberglass surface, but you'll probably have to plan on yearly applications. Our current tests are set up to answer two basic questions about these products: Can you successfully recoat the surface without stripping off the old product? And how difficult is it to remove the product?

How They Work

There's nothing mysterious about restoring the appearance of a fiberglass surface. When the boat is new, the gelcoat is very glossy and has a uniform color. After exposure to sunlight and weather, however, the outer surfaces of finely divided particles of opaque pigment that are suspended in the resin change color from the effects of UV and oxidation. Degraded pigments tend to become lighter in color, turning a yellowish gray. Because not all surfaces are exposed to the same sun and weather conditions, the color becomes blotchy as well as faded. At the same time, UV rays and weather cause the smooth surface of the gelcoat to become microscopically pitted. A smooth surface appears glossy because almost all the rays of light that strike the surface are reflected back in the same direction; a pitted surface scatters the reflected light and appears dull.

Restoring the surface's appearance, then, involves two things: removing the discolored outer layer of pigment (it's not feasible to reverse the weathering process) and providing a smooth surface to restore gloss. Removing the outer layer of the pigment is a mechanical operation involving scraping or grinding off the surface layer with an abrasive. Sandpaper would work, but it's generally too coarse for the job making the surface smooth a much more difficult task. The more common approach is to use a very fine abrasive powder suspended in a liquid. If the abrasive is extremely fine, the mixture is called a polish; if the abrasive is somewhat coarser, it's called a rubbing compound. The more severely weathered the fiberglass, the coarser land therefore more aggressive) the abrasive should be. Slightly weathered topsides respond well to polishes; more severe weathering calls for compounding, followed by polishing. The objective, of course, is to obtain a uniform color. Once the color is uniform, the next step is to keep polishing the surface until it's as smooth as possible. It's almost impossible to obtain the microscopic smoothness that's required for a high gloss, but it's a good idea to remove as many small gouges and scratches as possible. The next step is to apply a transparent film that will fill the microscopic pits and valleys, leaving a smooth surface. Water ill do the job for a very short while, until the water evaporates. The trick is to find a material that will keep that "wet" look for an extended period of time. Wax is the classic choice. It does a pretty good job of providing a smooth surface and lasts for a good bit longer than water. In our experience, a typical wax job will last about three months. Some wax products--those that contain harder, higher-molecular-weight waxes can last up to about six months. These are usually paste waxes rather than liquids and are correspondingly more laborious to apply.

Fiberglass restorers use even higher-molecular-weight ingredients--acrylics or acrylic-urethane resins--as film-formers. These products consist of water-based emulsions of droplets of resins. When the water evaporates, the resin coalesces to a clear film that's insoluble in water. The emulsions have low viscosities-much like water or liquid floor waxes--and dry rapidly. These characteristics make for easy application but also mean that relatively little film is left after one application. Multiple coats are required, but the low viscosity means that application is easy, and the quick-drying means that you don't have to wait for more than a few minutes between coats.

Instructions for the products we tested typically call for about five initial coats, with three maintenance coats at the end of each year.

What We Tested

The eight products we're testing were selected after an exhaustive canvassing of boat shows, chandleries and catalogs. We looked for any product that claimed to restore fiberglass and wasn't a wax. We found seven do-it-yourself (DIY) restorers and one that's only marketed as a professionally applied product. Most of the products are sold as kits--cleaners, strippers, polishes, and final coat, or some sub-set of these. Most come with applicators and instructions of varying detail; one even comes with an instructional video, which seems to us to be carrying things a bit far. From our experience, all of the products are reasonably easy to use. One caution we'd emphasize (for all the products) is that the surface be clean and of a uniform color before you apply the clear top-coat.

The Tests

This year's testing was a continuation of a program started back in 1997. At that time, we took a series of well-weathered fiberglass panels that we had sawed from the hull of a wrecked sailboat and applied each hull restorer to a panel following manufacturers' instructions. In the case of Microshield, the only dealer-applied product, we sent a panel to the manufacturer, who applied the product. Prior to restoration, all the panels were mottled, with a dead flat surface exhibiting no trace of gloss. After restoration, all had been dramatically improved (see the chart above for initial gloss readings). Before exposing the panels to the weather, we tried placing a drop of water on each panel (a panel that's protected will cause the water to form a distinct bead, rather than spreading out to a shallow puddle). We also made judgments about each panel's appearance, and then measured the gloss level of each, using our own gloss measurement system that has worked well for us in the past. We made a mirror-image "yardstick"-actually only two feet long--and placed it perpendicular to the panel that was to be measured. We shone a light on the ruler, using a constant light source and a constant angle of illumination, and looked at the yardstick's reflection in the restored panel. The glossier the surface, the more of the yardstick scale was reflected, and the higher the number that could be read. We then left the panels outdoors on south-facing racks tilted to 45", and left them there observing their appearance periodically. After a year, we took the panels off the rack, washed off surface dirt with a soft brush and a solution of liquid dishwashing detergent, and tested for beading and measured the gloss again. We then divided each (except for the Microshield-treated panel) in half and applied three maintenance coats to half the panel, without removing the material that had been applied. We stripped the other half-panel down to bare fiberglass using the stripper provided with each product or, if no stripper was provided, with the stripper from another product. We then re-applied fresh restorer per instructions (usually about five coats).

We didn't do anything to our Microshield-treated panel. The product claims eight years of protection, and, in any case, we didn't have any material to recoat it with, because the panel was prepared by Microshield and not by us.

Our reasoning was simple: It's easier to add maintenance coats to an existing product, but we wished to find out if we could get a better appearance by stripping and recoating. We also wished to see if stripping was difficult, as some readers have said. The panels then went out to their racks again. Our test season was shortened somewhat by the necessity of moving our test racks from Connecticut to Newport, Rhode Island (our landlord in Greenwich, Connecticut, wanted his roof back), but we did get nine months of additional weather testing.

The Results

To summarize the findings in last year's report, all the panels still beaded water after a year's exposure, gloss had declined on all panels and all (except Microshield, which we didn't try) stripped easily. Microshield emerged with the highest gloss, followed--at a distance--by New Glass and Poll-Glow. TSRW and Vertglas also showed some gloss retention, while the other products had all but vanished, at least in a visual sense. The one wax tested--the now discontinued Boat Armor Microshine--gave up after a few months as far as gloss was concerned and wouldn't cause water to bead after six months. Don't be misled by the gloss numbers; even a minimal gloss (such as 1) is a vast improvement over no gloss at all.

We found that all the products stripped easily, with the sole exception of TSRW (whose QuickStrip didn't live up to its name, convincing us to finish with New Glass Stripper, which worked well). Sea Breeze didn't come with a stripper, so we used Vertglas stripper. We reported previously that poll-Glow doesn't come with a stripper. It does. We tried it on another section where it worked well. We also found that one can get about the same gloss after applying three maintenance coats to the weathered surface as we did when stripping the surface and starting from scratch. This year, after an additional nine months, the results compare to last year's on both recoated and stripped-and-recoated halves of the panels. Microshield is still holding up very well after 21 months. Last year's two winners in the DIY class--New Glass and Poll-Glow-again led the pack with respectable gloss retention. They were joined by Vertglas. When we first tried Vertglas we had applied it with a cloth, rather than a sponge applicator. For the recoating of the panel, we practiced with Vertglas' brush/sponge applicator and obtained both a much better initial gloss and a longer-lasting gloss.

Except for one product--Sea Glass Sea Protector--we could discern no real difference between the panel halves that had been simply recoated and the ones that had been stripped and recoated. The recoated side of the panel treated with Sea Glass Protector seemed a bit more milky in appearance than the side that had been stripped before recoating.


The best of these products work. They're not magic, though. If you insist on having your boat look new, the surest way is to buy a new boat frequently. Two-part polyurethane paints, such as Awlgrip, Imron and Interthane, will do a fine, long-lasting job ... at a price. A paint job with one of these paints will probably run you about $100-$200 per linear foot, if applied professionally. Expensive, yes, but in our opinion, a boat with faded gelcoat is a good candidate, sooner or later, for a paint job. Fiberglass restorers simply postpone the job and expense. Intermediate in cost as well as (probable) durability is Microshield. The cost of a Microshield job will depend on the size and style of your boat; we couldn't get a simple estimate from the manufacturer. If you're interested, you're best off contacting them directly. The DIY restorers generally sell for $35 to $60 per kit, which will handle a 25-foot boat. New Glass, Poll-Glow or Vertglas, our longevity winners, should provide reasonable gloss for a season in most climates. Application of three maintenance coats once a year should keep the boat glossy, if not new-looking. They all dry in minutes, so you can recoat by working your way around the boat and just keep going until you've completed three circuits. We've heard scattered reports of some of these products going milky, yellowing, flaking or cracking, as well as reports that stripping is difficult. In six years of testing products of this type, we've never encountered any of these problems. We've applied restorers to a variety of small craft that live outdoors, with no signs of trouble. This year we stripped a Sunfish sailboat that had been receiving maintenance coats of New Glass for the past five years. It stripped easily.

The one report we haven't been able to check out is that of yellowing. Unfortunately, the wreck from which we carved the test panels had a yellow gelcoat. For this year, we're planning on adding on some new panels in white and/or red. Should you use a fiberglass restorer on a new boat to provide added protection? We think not. You'd have to sand or scuff the surface to get the restorer to adhere well. Wax is a better choice.

For older boats that have become dull and streaky, however, fiberglass restorers offer an economical, inexpensive means of making your boat look shiny again, and keeping it that way for a reasonable period of time without an exorbitant amount of effort. Our picks are PoliGlow, New Glass and Vertglas, with TSRW close behind. Microshield is still the most effective product we've found to restore gloss to an old boat. If it holds up for a few more years, its higher price tag may well prove to be worth it.

Copyright Belvoir Publications, Inc. All rights reserved. April 1999