1999
Foam Roller Covers-It's Not the Color That Matters
by Philip Jacobs
Foam rollers are great for spreading and applying resin to a hull. Short nap (thin) rollers provide a faster, smoother, more uniform coating than a brush, reducing the amount of resin used, and the amount of sanding required after it sets.
Like many builders, I buy nine inch long, foam roller covers and cut them into thirds to fit an ordinary three inch trim roller, which fits better into hulls, and covers contours better, than the full length rollers. Like many builders, I've been warned to stay away from certain, unspecified, black foam roller covers which reportedly disintegrate as they travel across the hull, leaving a trail, not unlike brownie crumbs in a kitchen, permanently encased in epoxy.
West System sells seven inch long, foam roller covers specifically for use with their epoxies, which presumably work with other manufacturers' resins. However, these can be difficult to find on short notice, and may have to be ordered through a catalog.
I was pleasantly surprised when I found one brand of inexpensive foam covers at a local home center which specifically said they were for use with epoxies, along with other types of materials. These covers were yellow, like the West System ones (and unlike the black rollers of death), and they worked well for me on two boats. Empirically, it was clear; yellow foam rollers are 'good', black foam rollers are 'bad'; at least as far as epoxy is concerned.
However, when I picked up a different yellow foam roller cover at a different home center (all right, I'm a junkie) I was surprised when the label was silent regarding epoxy. My curiosity was also piqued by the white foam rollers, typically sold only as smaller mini-rollers with rounded ends. So over a year ago I wrote to the manufacturer, asking about the differences between the colored foams, and their compatibility with epoxy resin. I am still waiting for an answer.
Meanwhile, on one of my hardware store prowls, I discovered that one manufacturer of these products, Padco, is located in our own back yard; another 'Products We Use' company! Although it required 10 digit dialing, I sprang for a phone call over a stamp and spent some time with their technical and sales representatives, posing the tough questions.
The bottom line: it's not the color that matters. Most foams sold for use as painting products start out as a polyurethane based product, then are modified or processed into different polymers, according to intended use characteristics. The open celled 'filter foam' polymers are typically classified as 'polyesters' or 'polyethers', then into various use grades, and can be combined with a rainbow of different color additives.
Unfortunately, it's the more expensive, polyester foams which typically work better with epoxies, although the resins holding the foam to the roller core, and the specific formulation of the epoxy resins and hardeners themselves can be an issue, along with contact time, and a host of other factors. Foams may also vary physically in cell size, softness, density, and durability.
The type of foam used may not make as big a difference when painting with latex products; in a pinch, I've even used pieces of packing foam attached to scraps of wood with staples or hot melt glue, for a quick, disposable touch-up. But certain solvents can dissolve specific foams, and others can cause swelling of the foam on a polymer level. It's very difficult to tell the difference between a polyester and polyether foam, and this information is not likely to be printed on the label, so builders are advised to contact the manufacturers, or to try a sample with the resins they are using.
Builders should also pay close attention to the brand and product number they are purchasing; many of these items and packages look the same, and some manufacturers may even offer similar looking products in different foam grades for specific applications. This is another case of 'caveat emptor' (let the buyer beware), at least until we find out the Latin for 'let the builder beware'.
I did try several of the Padco products, including their white, mini-foam rollers (item 3818), which provided very smooth coverage wetting out plywood on a stitch-and-tape boat. I was almost tempted to try their special, nylon flocked foam roller (item 3721) for varnishing, but stuck with the traditional brush.
Cost can be an issue, because these covers must be disposed of frequently, unlike painting tools which can be cleaned and re-used. Although they are a bit more expensive per use than cut-up, standard foam covers, the mini rollers (about 1-1/4 inches in diameter by 4-1/2 inches long) can reach into some tighter spaces, like canoe ends, and the rounded tips can be run tight up against corners and edges without scraping coatings off of adjacent surfaces.
Since most builders pour the resin directly onto the hull, the smaller loading capacity of these covers is probably not of much concern in this application. Because the roller 'bearing' is encased inside the cover, and replaced with each new one, cleaning resin off of mini-roller frames is also easier. I didn't try the mini rollers over cloth, and there may be applications where the larger diameter, or shorter nap available on standard roller covers may be preferred.
If you are unable to locate a specific Padco product locally, or just want to check out the variety available, the company maintains a factory outlet store, open to the public, where any item in their entire line can be purchased, at 2220 Elm Street Southeast, in Minneapolis.
