|Forum topic by Mark A. DeCou||posted 11-24-2006 09:08 PM||18230 views||5 times favorited||18 replies|
11-24-2006 09:08 PM
For a reprint of the better, and expanded article, contact:
Bob Stover, Publisher
Using the Right Glue in the Right Place.
I’m not a chemist, and I’m not a glue seller. However, I am a glue user, and there are several things that I have learned that others might benefit from, so I decided to post some comments about glues. The type of information that I have learned on my own, and through reading.
In cases where I have learned about new techniques and products through reading, I seem to only feel confident with the information after I have tried it myself, so I am only providing information here that comes from my own experiences.
As with any tool, Glue is something that I have to learn to use right, learning the tricks by experience. This experience shows me where my assumptions were wrong in the past, and allows me to make adjustments in my techniques. About 10 years ago, I only had one type of glue in my shop, and it was a bottle of Carpenter’s glue, which I have learned since is called PVA glue. Over the years, I have developed techniques that require me to keep on hand various types of glues for each application.
I use PVA wood glues (Polyvinyl acetates) for all wood joinery, except loose joints, which I discuss below. These PVA glues are the same type that all of us use, in brand names such as Elmer’s, and come in either white, or yellowish colors. There is a shelf life of around a year, so I buy smaller bottles as I need it throughout the year. I prefer Woodworx PVA glue that I buy at Wal-mart. The price on this product has gone up a lot in the last year, and so if it continues to climb, I might be searching for alternative brands, or retailers.
I like Woodworx because it sets quickly, and any spill out when clamping will dry quickly. If I leave the spill-out alone for about 30 minutes it will easily scrape off with a scraper or knife point. However, if I leave it longer, such as over night, this stuff is tough to scrape off, and will pull out wood fibers when it releases when scraped. Also, if I try to wipe Woodworx up with a rag, it will be pushed into the wood fibers, and it is hard to get out so that the following wood stain process will darken the wood consistently.
On unstained wood, the dried spill-out glue will prevent the wood from absorbing the wood finish consistently, and a whitesh spot appears in the first coat of whatever finish I am applying. Normally, I find these white spots in my finish where I had a spot of glue on a finger when I touched the unfinished wood somewhere during the clamping process. When I find these small white spots in the finish, I scrape them out with the side of an Exacto Blade, and apply more finish, easily and quickly removing the dried glue spot, without sanding. I learned the hard way about 9 years ago to not spot sand a glue spot, as the spot leaves sanded fibers that are different than the adjacent wood, and the wood subsequent staining process will only highlight the flaw. Scraping with the small Exacto blade works great. When a blade is dull or gets too covered with dried glue to work well, I toss it, and get another out of the pack of new blades.
I prefer to never clean up PVA glue with a wet rag. Water thins the glue, and so I don’t want to introduce moisture that might weaken the glue, and also I don’t like to sand a project again. I use PVA glue on joinery after all of the boards have been final sanded to 220 Grit, and so I don’t like to wipe around with a wet rag at that point. If I keep the glue squeeze-out to a minimum with careful glue application, then the resulting spill-out can be scraped up in about 30 minutes as described above.
Another key glue that I keep on hand is the family of CA Glues, one brand name for this chemical is “Super Glue.” There are many different brands, but all in the same family of “cyanoacrylates”, thus shortened to “CA.”
I keep four kinds of CA glue on hand. I use Thin for crack stoppage, Medium for sawdust/CA knot filling, Thick for gap filling, and Flexible for times when I think I want the glue to be somewhat rubbery when dried. With this assortment, I also keep on hand a “Debonder” and also a spray can of “Activator”. When I first learned to use this CA glue, I used the Debonder to unglue my fingers occasionally. Over time, I have learned how to use it, to where this rarely occurs anymore, but is always a risk. Once, I actually glued the thumb and forefinger of both hands together. That was a little embarrassing for my wife to help me with. I have also learned to not hold the bottle lid in my mouth while trying to put the cap on. I missed the lid once, and quickly glued the tip of the bottle to my lips, not a pretty isight.
After reading once (forgotten source) that CA glue was first developed for first aid officers to stop bleeding of wounds during the Viet Nam war, I started to hold my fresh cuts closed and drop a small dot of CA glue over the cut. What happens is that the bleeding stops quickly, and the cut is sealed, not requiring a bandaid. It stings a little, but not bad.
Now, I am not a doctor, so I take no responsibility of any kind for someone doing something with CA glue that could be remotely associated with a health risk. I am merely stating how I have effectively used it to stop a bleeding cut, happily keeping me working along in the shop, and avoiding the worried questions of my children and wife when I walk in the house with blood dripping, as in the old days. Since I started using CA glue for this injury repair purpose, I rarely have to let anyone know I was injured in anyway, as my cuts are usually small and from carving tools, and easily sealed with CA glue. I would not use CA glue on a Bandsawn finger (another story sometime).
I have searched many places to buy bigger quantities of CA glue, to reduce the cost. I have settled on 4oz bottles from www.hobbylinc.com, where my research shows has the best price, and provides an excellent product in the brand name Pro CA. They ship quickly, rarely taking more than 3-4 days for a UPS package to arrive at my remote location. Here is an item number of the Thin glue if you are wanting to search for it on their site: “gpmgpmr6004.” They have a lot of different brands, sizes, prices, etc., so it can be confusing seeing the entire list.
When I want to speed up the natural curing of CA glues, I prefer to let the glue cure for a few minutes before spraying it with Activator. I have learned that if I let it air-cure for a few minutes, it will cure clear, with no white-ish color after I hit it with the Activator. The thinner the CA glue I am using, the shorter amount of time I need to wait. For instance, when using the Thick glue, I might wait an hour, or even over night, but only a minute for the Thin. I learned the hard way that if I quickly hit a Thick CA glue with Activator without waiting for it to air-cure a while, the resulting cured glue may turn out white, or at least cloudy, which shows up bad on Walnut, my preferred wood. When that has happened, I air-brush some paint over the white-ish color.
Air-brushing has given me a lot of help with my projects this year, and at some point I will write out all of the useful ways it has helped, and why every woodworker should consider having an air-bursh kit in their shop.
Back to CA glue:
I mix 2-Part Epoxy a little light on the activator, so that the final cured glue is not hard like plastic, but slightly pliable. This is why I prefer to not use the double syringe style epoxy packaging, as I can’t alter the amount of glue vs. activator easily.
I also buy epoxy from www.hobbylinc.com, as it seems to be the best price I can find in the size bottles I need for my typical projects. I don’t use a lot of it, so I don’t really want to have a gallon bottle getting old on my shelf.
I have also used Polyurethane glues for outdoor products, but choose to never use them on indoor products. One brand name I have used is “Gorrilla Glue. There is a misconception on woodworking self-help websites about using Poly glue on loose joints. I don’t recommend this, as the bottle label says to use the glue on tight joints. When Poly Glue cures, it does expand, but the expansion is a foam, not a hard material like Epoxy provides. I got some heat once from a couple of woodworkers on another website for suggesting they not use Poly glue on loose wood joints. So, don’t argue with me, just read the label.
Let me know what I missed, what questions you have, and what experiences you have that are different than mine, I will enjoy learning.
Mark DeCou www.decoustudio.com
-- Mark DeCou - American Contemporary Craft Artisan - www.decoustudio.com