Strong Like its Namesake
Written: Jun 07 '04
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Product Rating:
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Pros: Waterproof joints, strong as its namesake
Cons: Cost, cleanup
The Bottom Line: This is not the glue for light duty applications due to cost and cleanup, but where the need is, the value is great.
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| gamblin_man's Full Review: Gorilla Glue |
When this new glue hit the home market it was an instant sensation. It was touted to work indoors or outdoors, to be “The strongest glue on planet earth,” and to stick any two things together. The fact that Gorilla Glue is still a market leader attests to the truthfulness of those early advertising claims. As always, the truth falls a little short of the hype that introduced this product. In this case, though, it wasn’t very far short.
Gorilla Glue
Let’s look at the claims for this product. From their website are these claims:
“Gorilla Glue is the strongest and most versatile glue on the market today. We do everything technically possible to make our glue the finest, strongest and most pure adhesive in the world. It takes just 1/2 ounce of Gorilla Glue to cover one square foot. That's 3 to 4 times the coverage of other glue. In addition to being 100% Waterproof, incredibly strong Gorilla Glue bonds wood, stone, metal, ceramics, Corian®, styrofoam and more. Remember that this glue will foam 3 to 4 times its applied size, so a little goes a long way.”
More of the features and uses are available at http://www.gorillaglue.com.
The glue originally sold in 16 ounce bottles or larger units. You now can get 4 ounce and 8 ounce bottles as well. The value of these smaller sizes will become apparent later in the review.
This was the first home use entry of a glue type, actually adhesive, called polyurethane. Where I use it most, in woodworking, its major competition is yellow wood glue or sometimes a two-part epoxy. The typical yellow glue has water as its solvent base and creates adhesion through evaporation. Epoxy glue uses an adhesive and a second hardener to achieve results. Polyurethane glue uses water as a catalyst to create a chemical reaction that causes it to adhere to a surface and to harden. Both yellow glue and Gorilla Glue make a mechanical bond by finding pores and broadening the apparent surface area.
First let’s look at some of the differences between Gorilla Glue and its chief woodworking competitor, yellow glue. Open time is important when a complicated assembly is being put together. The open time is the time that you can easily rearrange the parts before the glue “grabs.” For yellow glue this is around 5 to 10 minutes. For Gorilla Glue it is at least 20 minutes. That makes Gorilla Glue the winner in this case. How long the joint must be under clamp pressure is different too. For yellow glue it is an hour, I double that for Gorilla Glue. Both will cure to full strength in around 24 hours.
Then there is the impact of moisture, particularly in the humidity of the air. For yellow glue, high humidity slows the curing process because the air is nearer saturation and can’t wick off the moisture as well as dry air. Since Gorilla Glue uses water as its catalyst, the opposite is true for it. In low humidity conditions a little moisture has to be added at the joint to assure a strong joint. High humidity has no adverse impact. Speaking of moisture, Gorilla Glue is impervious to water. After it is cured, joints can be in standing water. For yellow glue, even the outdoor variety, the joint is moisture resistant only and will fail over time if immersed in water.
How about oil? Some of the imported woods (exotics) are quite oily. Polyurethane doesn’t use the same adhesion methods as its competitor and seems to hold just as well on oily wood as on other wood. I bought my first bottle of Gorilla Glue just after it first arrived at my local woodworking toy store. I watched them try to break a joint in oily teak that they had glued end-to-end the day before. They had not tried to remove the oil from the surface first. The joint held and the wood broke near the vise jaws. This isn’t to say that you needn’t be careful about hand oils on the joint or other impurities. The joint needs to be smooth, strong, clean, and just as well fitting as for yellow glue. You just don’t need to wipe the joint with an oil remover before application like you do with yellow glue.
This brings up another point of importance in gluing, gap-filling properties. The old standby, yellow glue, is notorious for needing well fitting joints. In other words, its gap filling properties are negligible. That is where the two-part epoxies come in handy. Gorilla Glue is not much better. Although polyurethane glue expands considerably during the curing process, it is not a homogenous expansion and doesn’t add much strength where there is more than a few mils of gap.
Clean up of the glue joint and surrounding area is always something to consider. Yellow glue, being water based, cleans up well with a damp rag before it sets up. The tools used in its application also clean up well in water early after application. Gorilla Glue, on the other hand, uses a chemical reaction to cure and requires a solvent, like alcohol, to clean it before it sets. After it sets, the removal process from tools is arduous at best. The manufacturer claims no known solvent will remove the cured glue. After the glue has dried, the expansion during its cure will usually leave a bead of brownish spume above and around the joint. It does not seem to penetrate the wood or its pores. It comes off readily with a sharp, flat object and leaves a clean joint with the surrounding wood still able to take a stain. I have sharpened a flexible 2 inch metal spatula to a more chisel-like edge (but not nearly as sharp as my chisels) for this task. My first use of Gorilla Glue was to add strength to a piece of pre-made kit furniture. I applied it like I would have yellow glue. That is a bad idea. It took a LOT of work to get all the foam off. The color is a little more brownish than yellow glue and is more noticeable on light woods like maple. It takes stain no better than yellow glue or epoxy,
How about economy? The purchase price of an equivalent weight of yellow glue and Gorilla Glue is in favor of yellow glue at about a three or four to one ratio. Gorilla Glue, on the other hand, only requires a small amount on one surface to make a solid joint. In low humidity conditions or when using the glue for non-porous materials, giving both surfaces a light mist of water significantly improves adhesion. Yellow glue needs a smooth, thin coating entirely covering both surfaces. So the difference in cost isn’t as great as it might seem.
The other issue is shelf life. The shelf life of either, before it is first opened, is quite satisfactory, around three years. Yellow glue does need protection from freezing, however. After opening, moisture gets involved. The opened shelf life of yellow glue is at least a year. Once Gorilla Glue is opened, it begins to catalyze from the moisture in the air that is introduced. It usually becomes unusable within six months. That is because the surface has cured deeply enough that you can’t get to the portion still uncured. I make a holder that lets me store my Gorilla Glue upside down. This doesn’t stop the curing process, but puts the cured glue above the spout, making the uncured portion still available. This can get you by for an extra three months or so. My first 16 ounce bottle of Gorilla Glue sits in my cabinet with a couple of ounces used, fully cured, as a reminder.
Considering the cost of polyurethane glues, it is best to buy it in a size that you expect to use in two or three months. That’s why the smaller sizes becoming available are important.
For uses other than wood, most of the things I have already talked about apply. I have used it to glue ceramics, metal castings, wood to plastic, and glass to glass. I have had mixed success with plastic to plastic joints. The same cautions already discussed also apply with these choices. In some cases, the color of the glue bead is more objectionable.
Conclusion
I still use yellow glue for most of my routine glue-ups in the woodworking shop. I keep a small bottle of Gorilla Glue for when the extra price is offset by the need. When I’m doing an outdoor project I buy enough more to do that project.
Recommended:
Yes
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Member: Larry
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