Putting the "log" back in Blog

A “Creepy” Tale for WIA 2012

Posted on September 28th, by Andy Brownell in Gorilla Glue, marketing & promotion, Wood. 1 Comment

maple boards ready for glue creep testAs a member of the online community loosely identified as “woodworkers”, I’ve been fortunate enough to develop a relationship with Gorilla Glue here in Cincinnati over the last 4 years. Additionally, as a professional in the marketing and advertising industry, I’ve been able to combine my professional know-how in digital marketing and branding. So is the case with my ongoing analysis of “glue-creep”

The year-long study I’ve been conducting in conjunction with Gorilla Glue is around the phenomenon of Glue Creep (or what some people refer to as glue line telegraphing) and has been a multi-stage review on a variety of factors that contribute to this puzzling and often elusive scenario.

Before Gorilla Wood Glue came along, I used Type II PVA wood glues like Tite-Bond. But now, many of the pieces in my  home were assembled with Gorilla Wood Glue, and they all have remained intact as you would expect. Regardless of adhesive brand you pick, glue-creep has been shown, and acknowledged by multiple manufacturers and consumers. This is based on what I’ve read and personally experienced through calls to customer service at the major brands.

As a caveat, wood is cantankerous and often unpredictable. It will do what it wants, despite all efforts to understand it. Based on our research, as well as a wealth of information available to the online woodworker, there are roughly four key principles that will impact the integrity and performance of any adhesive in woodworking that should be kept in mind.

1. Clean and flat surfaces to be bonded are the foundation of a good glue-up.

Glue is not a substitute for poor joinery. The strength of just about every joint relies on a good wood-to-wood bond (including clamping strength). Glue is not a filler, and shouldn’t be used to make up for sloppy work. That’s what epoxy or wood filler is for.

2. Wood is a bundle of straws. Dead or alive it responds to the environment. Glue-up and assembly strategies always need to reflect this.

Wood once was a living organism. Jeff Miller, in his new book “Foundations of Better Woodworking” uses the analogy of wood’s cellular arrangement like that of a big bundle of straws. That bundle reacts to changes in temperature and humidity as much in the form of a table top, or mortise as it did when it was a tree rooted in the ground (to a lesser degree of course). Some species simply move more than others.

3. Whenever possible, mate boards of similar grain orientation together when the glue line will be exposed (panels, table tops, etc.)

Wood’s relative movement based on grain orientation also can impact what happens along a glue line. While this is more visible on a table top or panel glue up, it happens in lots of other scenarios as well. Flat or Rift sawn versus quarter sawn have very different things going on. When exposed to seasonal (or in our case lab driven) environmental changes, one piece may shrink, while the other will expand. This is less about glue-creep, and more about two pieces of wood whose thicknesses have changed. This produces a stepping effect from one board to the next.

4. If what you are gluing up will be exposed to water or dramatic changes in environmental moisture, you may be better off not using a water based glue, especially Hide glue.

Generally, the chemical components of an adhesive will often impact how the adhesive performs before, during and after glue-up. For example, adhesives that are water based (PVA) or water soluble (Hide glue), will in general be more sensitive to environmental moisture than adhesives that are made from chemicals like polyurethane (Gorilla Glue). This is where claims like water resistant, versus water proof come in. Frankly, if moisture comes into the equation at all, I’d avoid Hide glue all together.

These are the most significant factors that led to our findings. I’ll be sharing this more in-depth at the Gorilla Glue booth at WIA in Cincinnati this November. Stop on over if you’d like to say hello or talk about glue-creep, woodworking or anything else. And don’t forget the “trade in for tough” program: bring in an old or new bottle of any competitive product and we’ll give you a bottle of Gorilla’s PVA wood glue at WIA in October and November!

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