Defining

Perhaps the problem starts with the question, "What is dry?" If you read labels and literature, you find phrases such as dry to the touch and new coals can be applied after X hours and dries dust free in X minutes. These phrases suggest that there is more than one condition called "dry." In fact, there are about half a dozen identifiable stages, although actually, drying is a continuous operation. Different materials and different formulations act differently during drying, but here is a general description.

First, the material is liquid immediately after application. Then it gets tacky. When tacky, it doesn't come off if you touch your finger to it. but you will make one heck of a fingerprint by doing so.

Next the surface dries so that it is no longer tacky. This is the "dust-free" stage, which means that dust falling on the surface will not absorb into the finish material but w ill stay on the surface, where it can be brushed away later. At this time, it is also, "dry to the touch."

Material under the surface dries next.

and when the full thickness of the coat is dry, you reach the first stage of true dryness, But this still isn't dry enough for sanding or for the application of additional coats.

Drying continues as the driers in the formulation evaporate from the material until the finish reaches what the Heath people, in their instruction manual, refer to as bone dry. This is the time for finish sanding or for the next coat.

There is another stage of drying, after the last coat has become bone dry. This final stage is sometimes referred to as curing. The finish continues to dry for days and weeks, slowly settling down to its final thickness. We think it is a good idea to wait for a week or so to apply wax or polish in order to allow ample time for this curing to take place.

The important thing to know about drying is that the surface should be bone dry before you sand it or before you apply the next coat. One of the most common of all errors on the part of finishers is the application of a new coat before the previous coat has dried sufficiently.

If you have doubts about whether the surface is dry enough, play it safe and wait. You can't go wrong by waiting; you can create problems by working on the finish or coaling it too soon.

Give the detail work the attention that the piece deserves. Here we round the edge of the butler's table to match the curve ol the leaves.

Note on some finishes Somepoly-urethane and other finishes dry with such a hard surface that a second coat cannot grip the surface properly. The labels on these finishes tell you to apply a second coat before a certain time has elapsed. If you wait longer than the specified time, then the surface must be sanded to provide "tooth" for the next coat. This is typical of enamels and other very hard glossy finishes, This really isn't a problem, since you should sand between coats anyway. It just means that the sanding must be,done and should be a little more thorough than you might otherwise do.

Wood Working for Amateur Craftsman

Wood Working for Amateur Craftsman

THIS book is one of the series of Handbooks on industrial subjects being published by the Popular Mechanics Company. Like Popular Mechanics Magazine, and like the other books in this series, it is written so you can understand it. The purpose of Popular Mechanics Handbooks is to supply a growing demand for high-class, up-to-date and accurate text-books, suitable for home study as well as for class use, on all mechanical subjects. The textand illustrations, in each instance, have been prepared expressly for this series by well known experts, and revised by the editor of Popular Mechanics.

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