Adam Savage’s definitive guide to every kind of glue
Excerpt: Every Tool's a Hammer
The following is an excerpt from Adam Savage’s new book, “Every Tool’s a Hammer.” Read or listen to it below.
The glues in my shop
Everyone has glues that they prefer, and I’m no exception. Over the years I’ve learned about and incorporated many glues into my arsenal of adhesive solutions, and I’m excited to share them with you. Just please take into account that my knowledge of these glues and their functional properties is just that—functional. They are the conclusions of an experimental generalist. I am not a chemist, nor a physicist, nor a material scientist. And there are exceptions to every single rule I outline below. You may meet someone who tells you there’s a better solution to every use case I outline. Go ahead and take their advice seriously and try it out for yourself. You may justifiably disagree with some of the glues for which I have great affection. That’s fine! It simply betrays, in the best way, the limitless land of possibilities when it comes to the developed ingenuity of humans to modify their world.
This is the biggest category—glues that, when exposed to air, dry out to create a bond. These can be water-based, like PVA glues (Elmer’s, basic white glues, wood glues) or solvent-based, like many “all-purpose” glues.
PVA glues are awesome and incredibly useful. Wood glue is one of the few things that does what it says it does just as well as you imagine it might. It produces a solid bond, with high strength and flexibility. White glues, like Elmer’s, are also phenomenal when using them on the porous materials for which they’re best suited—stuff like lightweight paper and corrugated cardboard. A new, thinner formulation of PVA glues (a main brand is called Mod Podge) has become invaluable for people who make things—props, costumes, models—out of foam. These glues are waterbased, which means they have no noxious chemicals that stink up your house, and are easy to clean up.
These are a constant source of disappointment to me. I’ve been let down so many times by “all-purpose glues” that they deserve only the briefest mention here. Sometimes they’re plastic solvent-based, like Duco Cement, sometimes they’re silicone-based, but they’re almost always in my opinion a temporary solution. Some people swear by them, I’m not one of them. Your results may vary.
I really like contact cements. These rubber-based glues also flash off their solvent base to dry, but are applied in a different way. Contact cements are mostly used by applying the glue to both surfaces being joined, letting the glue set for a short while, but not too long, and THEN joining the surfaces together. Blow-dryers are good for accelerating the drying process with contact cement. I use them all the time in my one-day builds for Tested.com when whatever I’m building involves a fair amount of glue-up.
When properly applied, this stuff can work miracles. They put shoes together with it. That should tell you something. Indeed, this family of glue makes tough, strong, yet flexible bonds suitable for everything from shoes to foam to attaching posters on board. For porous materials, I often use two coats of the glue on each side. In the right application, this can be one of the most powerful glues for gluing dissimilar materials together as well. Contact cement comes in tubes, cans, and even spray cans. I’ve used them all. My favorite contact cement is called Barge glue. A favorite among leatherworkers, I’ve found it to be properly tenacious. However, the cheap generic contact cement you get from your local mom-and-pop hardware store has rarely failed me, either.
Courtesy of Simon & Schuster
Hot glue is a thermoplastic substance. That means it is highly reactive to heat and cold and moves a lot with temperature variation. At room temperature it is a moderately flexible plastic that comes in stick form. When you feed the glue stick into a glue gun with a heating element, it comes out as a thick, hot, honeylike liquid. As it cools, it sets.
For quick and dirty builds, hot glue can’t be beat. For anything that you want to last, I would tend to avoid hot glue like the plague. (I’ve had things that were hot-glued together just fall apart while mounted on a wall, for instance.) Hot glue works best for porous things like wood and cardboard—it’s AMAZING for cardboard—and terrible for nonporous things like metals and glass.
Hot glues most often come in a clear or translucent form, but can also be bought in colors. I’ve used red hot glue for doing fake wax seals on theater props like old-timey envelopes. There are also low-heat variants of hot glue, which can be great when you’re gluing something like Styrofoam or foamcore board that melts easily. Hot glue can also be used to make castings. I know of a theater show that needed chicken legs for a dinner scene and the scenic department used hot glue squirted into a silicone mold made from an actual chicken leg. While I’m certain it didn’t taste just like chicken, the end result weirdly felt just like chicken.
Epoxy 2-part glues
These are thermoset glues wherein you use two separate liquids—a resin and a hardener—and mix them together to create an exothermic (heat-generating) reaction that chemically sets the mix. Two-part epoxies are often brittle glues, but there are more flexible formulations out there as well. They often come in the classic “5-minute” glue form in a pair of tubes with a plunger. Unlike a thermoplastic glue, epoxies are permanently set once they’ve hardened. They cannot be remelted with the application of more heat.
Epoxies are a great nonsmelly product to use with fiberglass. Boats around the world are built using glass matte and epoxy resin. All the ships in the original Star Wars were put together largely with epoxies. The big downside of epoxies is that they can be quite bad for the human body, so make sure you use gloves and work in a well-ventilated area when your project calls for it. And if you’re using large amounts of epoxies, for coating something or fiberglassing, use a chemical respirator. JB Weld is a particularly fine tube-based example of these glues. There are even (plausibly apocryphal) stories about it holding a motorcycle crankcase together long enough for the bike’s rider to get to a repair shop.
Also a thermoset adhesive, epoxy putty is a big family of glues that can join things but can also be used as a maker material in its own right. There are versions for plumbers that can be applied around leaky pipes. Others are made to repair leaks on boats. There are versions formulated specifically for metals, for woods, and for plastics. There are super lightweight versions, too. Because they come in a claylike form, they can also be ideal for one-off constructions.
Like the glues, epoxy putty has two parts, often in two different colors, each the consistency of clay. Take the two parts, knead them until you have created a third color and can’t see either of the original colors, and then put the putty to use. Some set fast, others set slow. I’ve used epoxy putty to make dollhouse bathtubs, fantasy gun grips, and even file handles. Once they’re set they can be sanded, cut, and even screwed together with common woodworking tools.
Often referred to by the brand name Krazy Glue, this class of glue, cyanoacrylate, is the soul of the special effects industry. It was originally formulated as emergency battlefield sutures during the Vietnam War and I know model makers who swear by CA glue for stitch-worthy cuts (I’ve never tried it). Lorne Peterson, one of the original model makers on Star Wars and an old friend, was the one who discovered CA glue as an Eastman Kodak product and introduced it to the ILM model shop. It’s import in the special effects industry cannot be overstated. CA glue is highly versatile and comes in liquid form with varying degrees of viscosity, from the super-thin (very tricky to use right) to the super-thick gap-filling kind, to the newest version, flexible CA glue, which I’m just starting to use, and like a lot. All of them can set when exposed to air or be accelerated by adding a “kicker.” Once set, it becomes a hard acrylic that tends to be brittle, so you want to be careful.
Super-thin CA glue deserves some extra attention here because it’s so thin (like vodka) that it flashes quickly and sets almost instantaneously, way faster than any other CA glue formulation. It’s amazing for things like ceramics, where it can wick into the porous ceramic and leave almost no trace of itself. But if you have your skin anywhere near that crack, it’ll wick underneath your finger and glue you to the very thing you’re trying to fix. The fact is, few glues can get you into more trouble more quickly than a super-thin CA glue. I have glued hero props to my own hand with super-thin glue more times than I care to admit.
It’s not just your own skin you need to worry about either. You have to be vigilant with the entire surface of the object to which you are applying it. Working on a commercial for Jamie back in the mid-90s, I spent a week making brass corners and filigree for an incredible glossy lacquered box that my colleague Lauren built out of hardwood. On the day of the shoot, while trying to hold down a recalcitrant brass corner, I used super-thin CA glue and it wicked into the joint, and then ran right down the front of the prop, on the camera side. I still remember the feeling in the pit of my stomach. Jamie was pissed, and when Jamie gets pissed, he doesn’t show it much in his voice or his manner, instead his head turns bright red. He’s like a human thermometer, with a mood head. He ended up having to use crayon wax that he mixed and formulated to match the lacquer finish to hide my glue streak from the camera, and he had to redress it for every shot. His head was bright red the whole time!
Long story short: super-thin CA glue, beware. CA accelerators are what is referred to as “kickers.” They are solvents that can be added to typical CA glues to accelerate their setting time from minutes to mere seconds. They come in spritz bottles and spray cans, and can also be applied with a needle applicator. They can be amazing when you’re doing quick and dirty model work, especially in films and commercials; you just have to remember that solvent-based CA kickers can often have a deleterious effect on paint jobs and on clear plastics (beware of kicker and polycarbonate!). So as with any unfamiliar process, do a test first on scrap material to understand a CA accelerator’s effect on your build. You don’t want to do anything you can’t fix later.
Little known fact: baking soda is also an excellent accelerator for CA glues. It kicks them almost instantaneously, and it doesn’t really smell at all. Sprinkling a little bit on glue you’ve laid down also makes it immensely stronger. I’ve used baking soda and CA glues to create gusset-like welds on the inside of styrene boxes that made them incredibly strong. I have known plenty of model makers over the years who can’t abide the smell of solvent kicker and only use baking soda.
These are a special class of adhesive. A weldbonded glue melts both sides of the bonding equation and then dries out effectively making one part. This is why it’s called a “weld.” Weld bonds are absolutely fantastic for gluing together acrylics and other plastics. Model airplane glue is a thickened type of plastic weld bond, but it also comes in a much wetter form used for making things like acrylic boxes. The glue that plumbers use for joining PVC piping together is a weld bond. I love weldbond glues, they create strong joints, and they do their work fast. There are different formulations of weld bond for different types of plastic. There are weld-bond glues for ABS, polycarbonate, and PVC. I tend to use styrene and acrylic mostly in my shop, so my glue of choice is Weld-on 3. For styrene scratch building or putting small pieces of plastic sheet together, there’s nothing better than a bit of Weld-on 3 and a brush.
PopSci’s special Q&A with Adam Savage
Q: This book is, in many ways, immensely practical, from a taxonomy of glue to full-page reproductions of your own project sketches. But it’s also deeply philosophical. What compelled you to tackle deeper themes like creativity and self-mastery?
A: I originally thought the book would be a lot more instructional. And then as I started to examine the limits of my knowledge (which are significant), I realized that I couldn’t pretend to be an authority on many of the skills that I know, but I do feel like I am an authority on how to combine them in interesting ways in order to get a project done.
Q: You’re not the only one offering advice here. The book includes musings from Nick Offerman, Guillermo del Toro, Pixar director Andrew Stanton, and others. How did you know they’d be such founts of wisdom? What did it take to incorporate their voices in your book?
A: It was actually easy to incorporate all of their voices into this book because the interviews that I did with them are simply extensions of the conversations I have with them as friends and colleagues. Each of the contributors to this book are amazing creators in their own right and also deep thinkers about their process, and it’s delightful to talk to them about it.
Q: People who are already see themselves, like you, as “makers” will probably naturally gravitate toward this book. But what about someone who’s never tried to bring a DIY project to life? What can they learn from “Every Tool’s a Hammer”?
A: What I hope someone who is not a maker takes away from this book is the courage to jump in and make something if they want to. For me, obsession is the beginning of every project and is the gravity of making, and for people who read this book, I want their hands to itch to get building.