Wood Glue is Your Best Friend

Lesson Learned:

Wood Glue is Your Best Friend.

I have stumbled on a number of posts on the internet discussing what kinds of glue to use when building a dollhouse. I can’t speak for everyone, but for me – plain old yellow wood glue has been the go-to adhesive

When in doubt, I use wood glue. I like the fact that it dries somewhat slowly, but holds very well, (so it’s easy to use) and it’s ridiculously inexpensive (I bought a gallon jug for $11). The downside to wood glue is that it’s not always transparent when it dries, it doesn’t take stain at all, and it doesn’t hold right away like super glue does. I have heard that super glue can get brittle with age, and might not end up holding as well over time – so I default to the cheap reliable wood glue for almost everything.

three bottles of wood glue
Hello old friend!

One of the issues I had before was trying to use wood glue that comes in the cylindrical squeeze bottle with a tip for dispensing the glue (the one on the left in the picture above). I like the idea of only pouring a little bit at a time. But that tip is usually too big for what I’m doing with a dollhouse. And invariably that tip gets clogged up, and I have to spend a half-hour scraping yellow boogers out in order to get it to flow again.

For this most recent dollhouse, I ended up pouring a little bit of glue into a small mason jar. I then used a popsicle stick or tooth pick to dab as much as I needed on the part I was working on. When I wasn’t using the glue, I could simply screw the lid on, and it was ready to go for the next time. This also saved me because I had have a habit of leaving the workshop thinking “I’ll be right back down.” When I came back two days later, I found the wood glue dried solid to the jar. In that case, all I had to do was pour some water in the mason jar, and wait a bit. The glue would turn into chunky yellow snot, and would come right out.

How does Wood Glue Work?

I started getting curious about what makes glue stick (and the age-old, why doesn’t it stick to the bottle… it does, see above.) so I hit the internets, and researched for about seventeen minutes. So, what did that rigorous journey through half of a Wikipedia article and some other website teach me? How does glue work anyway?

The simple answer is: magic.

The more complex answer has something to do with cohesion, adhesion, van Der Waal theory, adsorption, chemisorption, and general molecular doohickeries.

My (certainly incorrect) answer is: it turns wood into self-carving puzzle pieces.

I think wood glue works by absorbing into the wood, causing the soft bits to swell. When the soft bits of both pieces swell, they ‘smoosh’ into each other. Then, when they dry, the soft bits shrink to their original size, grabbing onto each other like molecular puzzle pieces. As a result, that yellow slick of wood glue is less a layer of sticky hold-em-sauce, and more of a molecular carver that shapes the wood to lock to itself.

If you clamp the two pieces while the glue is doing it’s thing, those fibers will interlace with each other more tightly, and you’ll get a stronger bond. If you don’t clamp the wood, the two pieces are going to push away from each other, and your join will be dependent on the sticky hold-em-sauce (which isn’t really that sticky after all.)

illustration of how I think wood glue works
This is probably wrong.

To put it another way, imagine you have two dehydrated sponges, shaped like hands. Put them next to each other, and drop water on them. As they absorb the water, they’ll expand, and push each other away. Then, when they dehydrate again, they’ll return to their original small shape, only now they’ll be far away from each other. Now, slide them back next to each other, and clamp them together this time. Now when you add the water, they’ll absorb it and grow, and the fingers will interlace because they have nowhere else to go. When they dehydrate, and you take the clamp off, those fingers will be interlaced, and hard. And the two sponges will be stuck together.

Glue-up Clamping Time

That brings up the last point about wood glue: clamp time. It seems intuitive that two pieces that are clamped together over night will hold better than two pieces that are clamped for a half-hour. And that’s probably true. But think back to those sponges, once they have dehydrated, they can be clamped for another decade, but they won’t be anymore interlaced than when they first finished drying.

It turns out the required clamping time on a glue-up is inversely proportional to the mass of the pieces that are being glued +  their density + the stress that will to be exerted on the join. I just made that up, but I did so with confidence, so you can trust me.

Because that is hard to understand, and probably wrong anyway – I say make sure your pieces are clamped for an hour. After that, you’re good to go. If you plan on leaning on it – clamp it over night.

fake math equation
This is certainly wrong.

 

 

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