Popular Woodworking 2009-08 № 177, страница 54

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A soaking rag is not the answer to removing glue squeeze-out. The best method is to scrape the seam after the glue begins to set.

Todaysome epoxy manufacturers provide static mixers that thoroughly blend the two together without applying additional heat.

Freeze-t ha w stabi 1 ily. Water-based glues are prone to freeze at 32° F and below. Some water-based gluesare designed to handle the occasional freeze/thaw cycle and others just can't. Freezing can breakdown the polymers renderingtheglue useless. Some PVAglues have a tendency to have a "cottage cheese" look a fter freez ing. 1 ft his happen s shake Or stir the glue back to its original condition once it has reached room temperature.

Dale Zimmerman, senior technical specialist at Franklin International (the manufacturers of Titebond products), told me I hai as long as you can stir your glue back to the way it was before it froze (no lumps), il will workjust fine. Thiscyclecan happen many limes wilhoul any real effect on the performance ofthe glue.

Working temperaturesor glues. When working with PVA it's recommended thai white glues be applied in temperatures higher than 60° F and yellow glues in temperatures higher than 55° F. The reason it needs to be relatively warm is because as the glue dries, the loss of water pulls the adhesive particlestogetherwilh enough force to form a continuous film. ITthe drying temperature is too low, the glue particles will not be lluid enough to unwind and entangle and form a tough network. The dried film in thejoint will appear whiterthan normal Thisisknown as "chalking." When chalk-i ng occu rs the glued j oint loses St rength and that could result in a failed bond.

Chemically reactive glues need heat to cure - the warmer the better. It's recommended that urea formaldehyde, super glue, epoxy and contact adhesive be applied in temperatures greater than 70° F. Polyure-thanes can go down to 50° F but will take much longer to cure.

Clean up/disposal. Cleanup with water-based glues is a little easier than with solvent-based glues. Most directions for PVA glues say that you can clean up the excess squeeze-out with a warm damp rag (not soaking) before the glue dries. This is probably OK, but 1 preferto let the glue dry and just scrape it off. Ifyou scrape it off before it getstoo hard there will belessofachance of pulling up small chunks of wood liber.

However I've witnessed lots of people who take wet sopping rags and just saturate the entire area around the glue joint with water. This just can't be good for the wood orglue. Manufacturers tell usthatmost PVA glues can be thinned with pure water by no more than 5 percent by weight orvolume. There isa huge difference between a damp rag and a sopping wet rag in the volume of water.

Wood by nature is hygroscopic - it's always seeking moisture. Once the excess water has thinned the squeezed-out glue Irom thejoint, the water that now is on the wood surface is contaminated with watered-down glue. As the wood absorbsthe water/ glue solution, it will "size" the woodaround thejoint and act just like a finishing conditioner that might inhibit the absorption ofstains.

Earlier we discussed several processes that glue goes through in order to become hard. All of those processes required the wood to dry in a very specific manner. A high volume of excess water can change the delicate balance of this process.

Solvent-based glues will have specific solvents that are recommended by the manufacturer, so you should always wear gloves when workingwith these glues. Urea formaldehyde can usually be cleaned up with water. Forpolyurethane and super glues, companies recommend thatacetone be used. And cleanup for epoxy glues varies accord-ingto the formulation.

The best way to avoid a waste-disposal problem is to prepare only theamount of glue needed for your job. If the glue is anything other than PVA or super glue, it is recommended that this product be disposed of by a licensed hazardous waste handler or saved for household hazardous waste collection. However, if the glue hashardened, it may be thrown in the trash destined for a landfill.

Safety Precautions

All glues in liquid form should be handled with care. PVA and hide glue are by far the safest and are considered non-hazardous. They can produce pungent smells and have aslightacidicpHthat could cause some skin irritation with prolonged contact.

Solvenl-based glues are much more of a hazard. It's a good idea to always wear gloves, eye protection and the appropriate type of respirator. Make sure you always have good ventilation.

These types of glues are skin and lung irritants and allergy-sensitizers, so they could cause burns to skin and eyes. Most of these are flammable or in part flammable, so extra care must be taken when working a rou nd furnaces wit h pilot lights or any kind of an open (lame

Epoxy, urea formaldehyde and contact adhesives use solvents that if inhaled inhigh concentrations present certain health risks. And poly urethane glues do not have solvents but can produce hazardous fumes ifLheyare exposed to extremely high temperatures.

Never use solvents to clean glues off your hands. Activators for superglue contain small amounts of solvent that rapidly evaporate. Super glue is considered to be of low toxicity, but its activators are generally flammable and hazardous. Instant glues bond so rapidly and strongly that even a little sloppinesscan result in an undesirable situation (wonder how I know that).

The final concern is workingwith glues after they have cured. 1 do a lot of grinding, shaping and sanding which makes a lot of dust. The se hard bits of resi ns can be brutal on your eyes and lungs. Always wear a dust mask and goggles to protect yourself from these cured particles, pw

Marc Adams is the founder ofthe Marc Adams School ofWoodworking in Franklin, Ind.. one of the largest woodworking schools in the ivorld. for details, visit marcadams.com orcall317-535-40t3.

60 m Popular Wood working August 2009