ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Sunday, April 14, 1996 TAG: 9604160007
SECTION: HOMES PAGE: D-1 EDITION: METRO
Sticking to those repair jobs around the house is not always easy, but when the repair involves sticking things together you can do it more easily and effectively by choosing the right glue.
Different adhesives are available for all kinds of uses in the home. Before you select your one, first assess your materials, the performance requirements and how strong the bond needs to be.
For gluing wood to wood, a number of adhesives will do the job. The most familiar ones are the polyvinyl acetate-based white glues (Elmer's, for example) and the yellow glues with an added aliphatic resin. White glue is generally regarded as a hobby glue. It is very flexible but has poor moisture resistance. Woodworkers use yellow glue because, among other things, it has better moisture resistance and is easier to sand than the white version.
Professional woodworkers and cabinet shops generally choose a more advanced, cross-linking PVA glue (such as Franklin's Titebond II ), so-called because additional chemical bonds form within the adhesive and give it superior strength and moisture resistance.
For almost any glue to achieve its best bond, the pieces to be joined must be closely fitted, clean, and dry. If the surfaces are uneven, use an adhesive with good gap-filling ability, such as a two-part epoxy. Epoxies have excellent structural strength and moisture resistance but only when fully cured. If you use an epoxy adhesive, the workpiece should be clamped and left alone for a curing period of 12 to 24 hours. Epoxies are also good for joining disparate materials, such as glass to wood or metal to ceramic. Their relatively high cost makes them most appropriate for small-scale applications.
An increasingly popular adhesive for small repair jobs is cyanoacrylate adhesive, popularly referred to by the brand name ``Crazy Glue.'' It bonds most substances extremely rapidly (including fingers) and must be used with care. The chemical bond is strong, but not shock-proof: it can often be broken by a sharp rap. If a bad thing happens, like gluing your hand to something, the solvent for this adhesive is acetone. If you don't have any around, an acetone-based fingernail polish remover will serve in a pinch.
Another handy adhesive is what is generically called ``construction adhesive.'' All construction adhesives are elastomer-based extrudable mastics (adhesives that can be made to flow under pressure) and are typically applied with a caulking gun. Construction adhesives are usually formulated to mate with specific materials, such as masonry products, drywall, metal and pressure-treated or untreated wood. Read the label and choose the one most compatible with the surfaces you intend to join. Because construction adhesives are elastomers, they do remain somewhat flexible.
If the bond will be subjected to significant shear force, construction adhesive should be supplemented by mechanical fasteners. As the name implies, these adhesives are not intended for finish work. Most of them have volatile solvents and should be used only in ventilated areas. Keep some paint thinner or turpentine on hand for clean-up.
The above adhesives will take care of most household requirements. There are also some specialty adhesives available, primarily for commercial use. These include formaldehyde-based adhesives and contact cement.
Urea formaldehyde adhesive (plastic resin glue) comes as a one-part powder activated by adding water. Its use is mainly for gluing up load-bearing beams and paneling. Resorcinol formaldehyde glue usually comes in a two-part kit and is used primarily for marine applications because of its high strength and solvent resistance. These glues should be used with care, as they do release formaldehyde gas while in the liquid state. Contact cement is used for gluing high-pressure plastic laminates to wood or particle board in the fabrication of countertops or laminate casework. It is now available in nonflammable solvent and water-borne versions, which give off fewer fumes and are much more pleasant to use than earlier products. Typically, a thin coat of contact cement is applied to both surfaces and allowed to dry tack-free. Then the surfaces are forced together under pressure applied either with a roller or by tapping with a block of wood and a hammer. Because of the instantaneous bond, contact cement has to be used with great care.
Finally, for those who like to repair old or antique furniture, old-fashioned hide glue still has its place. Hide glue is a protein-based powder derived from cattle hooves and hides. When mixed with water and heated, it forms a gelatin. Most pre-1940 furniture was assembled with hide glue and can easily be taken apart for repair by steaming the joints. Fresh hide glue bonds very well to old hide glue, and because it is protein-based, it accepts an oil stain just as wood does.
If you can't find hide glue by name, just buy some unsweetened gelatin at your grocery store; it's the same stuff, only purified.
LENGTH: Medium: 85 linesby CNB