Ask iFixit: How Do I Fix Sticky Plastics?
How To

Ask iFixit: How Do I Fix Sticky Plastics?

Last month, I pulled my old K-Mix USB audio mixer out of the bottom drawer, and it was covered with dust and sticky goo. The reason? Its soft-touch coating, which lends a luxurious feel to plastic surfaces when new, had deteriorated. So, of course, I set to fixing it. 

Sticking Point

Why do manufacturers use these soft coatings in the first place? One reason is that they really do feel great at first. Instead of hard, smooth, cheap-feeling plastic, you get a rubbery touch that feels pretty classy. And these coatings can also hide surface flaws from the injection-molding process. As a comparison, I have a pair of Genelec speakers in raw, unfinished aluminum, and they look great, but the aluminum surface is flawed, patchy, and shows sanding marks. It’s a look that many people dig, but that’s aluminum. Flawed plastic is less attractive. 

The problem with these materials is that they break down over time, and end up either tacky and covered in dust, or actually sticky, so when you touch them they feel gross, almost like you spilled juice or honey on them. To make plastics feel soft, manufacturers use compounding additives like oils, antioxidants, and stabilizers that can come to the surface over time and create a sticky feeling. This process is called plasticizer migration. It’s a problem well-known both in car dashboards and guitar knobs

Sticky plastic on the bottom of the K-Mix mixer

The best way to avoid this is to not buy soft-coated products. You can slow down plasticizer migration by keeping your stuff cooler—it happens faster at higher temperatures. But if you’re here, reading this, it’s probably too late for that. 

Also, it’s not always obvious which surfaces will break down. That’s because there’s not just one material that causes this. While soft-touch plastics are a likely candidate, other materials can get sticky too. Rubber stuff goes sticky through a process called “rubber reversion.” Turning the sticky sap of the rubber tree into car tires and game controller grips requires heating it with sulfur and other additives. This curing process, called vulcanization, makes the sap’s polymer chains join together into a strong, stretchy matrix. When those polymer crosslinks break down with time and heat, the rubber gets sticky again.

Nikon’s F100 film SLR, from 1999, has a pretty standard rubberized finish, for example, but it’s notorious for going sticky. I gave mine to my dad, and then, years later, he gave it back, and the rubber was tacky and unpleasant, and attracted dust. But I fixed it. 

Smooth Operator

As long as your sticky thing has no sensitive electronics, your best bet is to start the cleaning process with warm, soapy water. In a lot of cases, soap will loosen the migrated plasticizers and restore a non-sticky finish. 

If soap and water don’t do the trick, you could try baking soda: Add enough water to turn the baking soda into a slurry paste. Spread it on the sticky surface, let it sit for 15 minutes, and then wipe it away.

If it’s still sticky, you’ll need to find a solvent. Always be sure to test a small, unobtrusive area first: Depending on the plastic and plasticizers involved, a solvent could actually break down the plastic further and make it more sticky. For this reason, we recommend staying away from solvents if you’ve got a sticky car steering wheel.

The go-to solvent for cleaning up sticky plastic is isopropyl alcohol. Pure, or almost-pure, alcohol is good for electronics use because it is non-conductive. We have a full guide on isopropyl alcohol for all the details, but for cleaning purposes, here’s what you need to know.

Isopropyl alcohol dissolves oils, kills viruses and bacteria, and evaporates without leaving a trace. For cleaning sensitive electronics components, you want the pure stuff, 90% alcohol or higher. But for cleaning sticky plastics or rubber, you can get away with lower concentrations, because you don’t have to worry about anything shorting out with residue. If it does leave visible impurities from the water, you can just clean again. Take a look at the list of ingredients: Whatever you’re using should be nothing more than isopropyl alcohol and water. “Rubbing alcohol” often includes fragrances or other chemicals that might not play well with your gadgets, and they will probably also leave a smell (even though it may be a smell you like). 

Trying to scrape off the sticky plastic coating with a Jimmy
The K-Mix’s sticky plastic, mid-scraping.

For the Nikon’s rubber, the fix is to gently rub it with isopropyl alcohol. Avoid drips, and go slow. It may take multiple applications to fix, but eventually, the rubber will stop feeling sticky and instead feel like, well, like grippy rubber. Pro tip: don’t use toilet paper when cleaning with alcohol, as it disintegrates immediately and just adds to the problem. I use squares ripped from old cotton t-shirts, and they work well.

For the K-Mix mixer, pictured here in all its sticky-finished shame, the situation was more dire. Even after an isopropyl rub, the coating stayed tacky. As you can see, I was able to scrape much of the coating off and then use isopropyl alcohol as a soak/scrub to finish the job. 

The underside of the K-Mix mixer, cleaned of its sticky residue
After the scraping and isopropyl soak: Much better.

The best way for this particular job would be to disassemble the entire unit to remove just the case, scrape it (with a plastic scraper like a Halberd spudger or plastic card, preferably, so you don’t scratch the surface), and then soak the case to remove the remainder. 

Other Solvents

Light naphtha: Not just for fire breathing. Image via Robert Trudeau.

Sometimes, however, alcohol isn’t the answer. For example, if you remove the paper labels from some food jars, the residual glue is best removed with lighter fluid, aka light naphtha, the kind of fuel you’d drip into a Zippo lighter. But if you are using lighter fluid to clean something other than glass, you should definitely test it first, to make sure it doesn’t destroy the underlying plastic itself. 

One fun fact about lighter fluid is that it is safe for cleaning vintage electric guitars with their delicate nitrocellulose lacquer finishes. But in that case, you should definitely avoid acetone, which will “melt” the finish (anecdotally, you might also avoid DEET-based insect repellents while playing outdoor gigs, for the same reason). 

Acetone, best known as nail polish remover, has its uses. We use it in our adhesive remover, for example. But it can damage ABS plastics, which is a shame because it’s pretty great at dissolving all kinds of unwanted coatings.

Liz’s soft-touch water bottle, sticky with migrated plasticizers (left) and after a wipe-down with an orange oil-soaked rag (right).

Orange oil is a popular solvent for scraping away adhesive residue (and it’s one of the things that makes popular adhesive removers like Goo Gone work). After seeing some reports of its effectiveness at cleaning up sticky plastics, iFixit sustainability director Liz Chamberlain tried it on a water bottle that used to be soft and became sticky. A wipe-down with an orange oil-soaked rag, then a rinse, made the finish on the bottle visibly smoother and no longer tacky. 

The only way to know which solvent or method will work on your particular sticky plastic item is to test it. Start with isopropyl alcohol, which is pretty benign to gadgets, and go from there, testing on a hidden spot before committing. 

As for safety, avoid breathing in fumes, wear gloves, and use in a ventilated space. Dispose of all cleaned-off gunk correctly, and be careful with those solvent-soaked rags, because they’ll be a fire hazard.

And if all this seems like a major hassle, that’s because it really is. Once you’ve scraped and de-gunked one gadget, you’ll be a lot less likely to buy a soft-touch product ever again.

This is the latest in a series of answers to common repair questions: How do I stop stripping screws? Should I even bother trying to fix this stupid, busted printer? I spilled liquid on my laptop—now what? If you’ve got other broad repair questions you’d like us to answer, leave a comment below.