Efficient Exterior Wood Prep

How to get the most from scrapers, abrasives and heat.

The most challenging and important part of painting exterior wood is almost never the painting itself. The real trick is creating a paint-ready surface beforehand. This fact applies to both brand new wood and previously painted wood attacked by the ravages of sunlight, moisture and seasonal temperature changes. These forces are why flaking, bubbling and peeling is always worse outdoors than inside. Although there are effective tools for this kind of surface prep, there’s no magic bullet. Successful, efficient surface prep involves finesse and knowledge that’s not immediately obvious. Many painters would do better at surface prep if they had more detailed insights about choosing prep tools and maintaining them. That’s what this article is all about. Put this knowledge into practice the right way and it’ll save you time and help you make more money.

Although it’s not essential to remove areas of old paint that are rock solid, you must go back to bare wood in places where peeling, bubbling and cracking is even a little visible. This is a given. You might even consider removing solid old paint in the interests of making your new paint look its best. The ridges left where old paint remains can make new paint look bad. Either way, you’ll need to experiment to deter-mine with the main surface prep tools below to see what makes sense for a given application. Each job is unique.

Scrapers for Bulk Paint Removal

While every experienced painter knows about the different designs of scrapers, too few understand how to make these tools fully effective. It all comes down to sharpening. Start using a brand new scraper of any kind and it’ll bite well. An hour later, not so well. A day later and you’ve probably lost 50 per cent of your former efficiency. Maybe more. To optimize scraper effectiveness, you need the tool to remain at or near peak sharpness. Scrapers with replaceable blades are one option, but learning to resharpen scrapers is at least as effective, and in some cases faster and more economical than replacing blades.

A sharp file, a belt sander and a bench grinder are three tools for sharpening scrapers. You’ll find a 10″ mill bastard file with a wooden handle is perfect for sharpening scrapers as they sit in a vise. Store the file wrapped in a cloth or inside a leather sheath because banging around in a tool box dulls a file faster than hard use.

An ordinary woodworking belt sander is another option for sharpening. Lock it upside down gently in a vise or a workmate and you’ve got a great way to sharpen scrapers. A 120-grit belt does the job perfectly. Remove the dust bag and do the work outdoors to eliminate any fire hazard caused by sparks.

Possibly the best way to sharpen paint scrapers is with a bench grinder, but don’t use the grinding wheel that comes from the factory. It’s too coarse and it causes too much heat build up. A cool running wheel is far better. It allows more precision and it generates far less metal-damaging heat.

Regardless of the tool you use to sharpen scrapers, look closely at a new scraper blade to show you the optimal angle to aim for. Most scrapers are ground to a fairly steep bevel, anywhere from 60o to 85o. Copy what you see.

Surface Prep and Your Bottom Line

As a painter you’re in business, and every profitable business opportunity sits behind a wall of difficulty. The higher the wall, the bigger the profits on the other side. The lower the wall of difficulty the more competition exists, driving down prices and profits. In the case of exterior painting, the wall of difficulty is mostly about the challenges of surface prep.

To win the most profits out of this challenge you need to do three things. First, you must convince your client that proper surface prep is key to a long lasting paint job.  You have to differentiate yourself from slip-shod painters out there who simply pretend to do surface prep but really don’t get it done at all. Second, you need to become efficient at surface prep operations. And third, you need to bid accurately on exterior jobs. If you take the “safe” way out and strike a deal on time and materials, the project owner gets all the gains from the hard-won surface prep efficiency you’ve learned. And if you do bid but bid short, you’ll make less money than you should have.

Heat for Softening Paint

This is one of the best ways to soften solid layers of old paint to make it easier to scrape, but heat poses risks. Traditional paint-softening with a propane torch and flame spreader is effective, but poses a fire hazard. A propane flame also vaporizes lead if it’s present in the existing paint layers because the process involves temperatures hotter than 1100oF. Any paint layer applied before 1978 could contain lead, and paint that’s older than 50 years almost certainly does contain lead.

Although softening paint with an open flame can fill your body with toxins, there are two heat-related approaches that are safe. One is an electric heat gun that operates below 1100oF. This is the vaporization point of lead. Keep paint temperatures lower than this and the lead stays in the old paint. An even more effective choice is the infrared paint stripper. It’s a handheld electric tool that uses glowing red heating elements to warm paint by “shining” on it. Soften an area, move the paint heater to the next spot, then scrape what you just heated while the new area is heating.

Abrasion for Final Prep

When it comes to paint prep, there are two kinds of abrasives: wire wheels and sanding disks. A wire cup wheel in a variable speed angle grinder is an aggressive tool for initial paint removal. You’ll find the knot-twisted version of the wire cup wheel the best for this application because the wires last longer and work better on loose paint. Straight wire wheels don’t last nearly as long and they’re not aggressive enough for most paint removal situations. You don’t necessarily need variable speed control on your angle grinder, but it’s a great feature. The ability to slow down the speed of the wheel is useful when working in close quarters or inside corners.

No matter what preliminary steps you used for strip-ping old paint, sanding the surface is the ultimate final step before repainting. That’s because nothing beats the right kind of abrasion for creating optimal absorbency on a wood surface. You can leave sanding out on some jobs if the budget won’t allow it, but sanding is always the best final step because it creates the ultimate paint-ready surface. The trick is choosing the kind of sander that’ll be effective, plus the kind of abrasive that creates the most absorbency.

For typical paint prep work, a hand-held 6” random orbit sander is ideal. Though a tool like this is just a little physically larger than the more common 5” random orbit sander, a 6” model is roughly twice as effective. Part of this is because it has a larger disk, but more than that is that 6” models have much more powerful motors. An 80-grit disk on this tool creates the best balance between a smooth surfaces that’s still rough enough to offer a good grip for paint. Too smooth actually reduces absorbency.

Exterior paint prep is like a combination lock. You’ve got to get all the details right for the lock to open. Combine the right tools and information with a commitment to detail and you’ll be better than aver-age at this essential exterior painting skill.

Mackinac Island – The Land of Painted Wood

Some places in the world don’t have much exterior wood, while others have it everywhere. Mackinac Island is definitely an exterior wood sort of place. It’s located in the Great Lakes region near the border of Canada and the USA and it’s covered in gorgeous buildings sided in wood clapboard and shingles. Many of these buildings are more than a century old, but even the new ones are required to follow architectural rules that demand exterior wood. Naturally, painting and repainting in a place like Mackinac is a way of life and the people there are good at it. Their prep trick? Just the basics of washing, heating, scraping and sanding. They also have a commitment to wood that shows up in the quality of the place. So next time you have a client who’s thinking of tearing off perfectly good wood siding just because they don’t want to invest in repainting, explain that the best wood buildings in the world aren’t covered in vinyl.[/textblock]

The Truth About Pressure Washing


A pressure washer is a useful prep tool for large exterior surfaces because it lets you cover a lot of ground quickly. But there are two reasons why a pressure washer alone is never enough. First, the spray stream doesn’t necessarily remove all loose paint. It can rip most of it off, but about 20% of flaky paint will remain because the high pressure spray stream is simply pushing it harder against the surface, not tearing it off. And second, no matter how carefully you use a pressure washer on a wood, it’ll lead to fuzzy surface fibers. This isn’t a problem as long as those fibers are removed with an abrasive before painting happens. The good news is that surface fibers raised by a pressure washer fall right off with just a quick pass of the right kind of sander if you let the washed surface dry completely first.

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