A common feature that hair dryer makers tout is the ability to make hair shinier. When we asked hairstylist Allen Ruiz about the best way to get shiny hair, he said: “Use a product that leaves the hair shiny and smooth.” Which is to say, shiny hair doesn’t really have anything to do with the dryer. Cosmetic chemist Perry Romanowski told us that the only things a blow dryer could do that hair products couldn’t were to “dry the hair more uniformly and keep hair straight.” Straight hair can be shinier hair: The cuticle—the outer scaly layer of a strand of hair—lies flatter, reflecting light. But even if your goal is to have shiny, straight hair, the only dryer qualities that will help you achieve that more effectively are good old “hot and fast.”

You’ll see plenty of features—ceramic coils, an ion generator, tourmaline—noted in marketing materials and pretty much every other dryer buying guide. But those are features of nearly all dryers. We visited the hair dryer section of Sephora twice while writing this guide and failed to extract any logical reason from the salespeople as to why their curated selection of designer dryers were better than other options. One thing that you should definitely avoid are retail employees who tell you that a $200 dryer is special “because it has ions.”

Ions are technically able to reduce frizz—but only frizz from static. Wet hair cannot hold a charge.

Mainstream magazines and hair dryer packaging commonly promote ions as a feature that makes hair less frizzy and more shiny. Hair dryers do produce ions, which are just particles (of air, in this case) that are charged (negatively, in this case). We found a report in which a high school physics teacher put an ionic dryer in front of a device that measures ions, and lo, it found something to measure (PDF).

But because almost all hair dryers are “ionic,” it’s hardly a thing worth debating, except for academic clarity. Our tests (below) didn’t show any meaningful difference with ionic settings on or off.

Our expert engineer’s opinion: “Ions? Please.”

Ions are technically able to reduce frizz—but only frizz from static. If you brush your hair while blow-drying it—or you just exist, in the winter months, depending on your hair—positive charge can build up, causing strands to repel away from your head and stick out. But wet hair cannot hold a charge. A blast of negative ions from the hair dryer on dry hair would bring it back to a neutral charge, but if you have a huge static issue, you can also just use a smoothing cream (which is easier to fit in a bag anyway) or a tiny bit of water.

Another claim regarding ions is that they can break up water molecules and speed up drying time. We couldn’t find any reason this would be the case, and neither could the engineers we spoke to. Doctor and prominent skeptic Ben Goldacre has questioned the ions-make-water-droplets-smaller phenomenon, too, on his blog Bad Science. Still, for good measure, we planned to test an ion-button-equipped dryer with and without ions in effect, just to see for ourselves if we were missing something.

Finally, sometimes makers of hair dryers with an on/off ion button claim that the feature is there so that you can use the dryer with the ion button set to “off” for fine hair to make it more voluminous. This could possibly work only if you were going for the kind of volume produced by static electricity.

The dermatologists we interviewed recommended ceramic-coated coils. They provide “a more even heat” than other materials, according to Melissa Piliang. All hair dryers work by heating up an element, such as a metal coil, and then blowing air over it, carrying the heat to your head. Ceramic material does heat up faster and radiate heat more evenly than iron or nickel. (Many space heaters also employ ceramic elements.) But the engineers we spoke to were skeptical that this component makes much of a difference in drying hair. Radiant heat isn’t really helpful “unless you expect to direct the heat far from the dryer,” said engineer Jim Shapiro, such as if you were trying to use a dryer to heat a room for some reason. Any heating element in a dryer gets the heat to your head via the blowing air. And though ceramic material does heat evenly, we couldn’t feel a difference in the heat coming from the dryers we tested with ceramic coils versus those made with other material. Regardless, you should move your dryer around as you do your hair, so the exact evenness of the heat coming from the dryer doesn’t matter too much. The bottom line is that most hair dryers have ceramic-coated elements anyway; don’t let a box’s claims fool you into thinking you’re getting something special.

Another material commonly found inside hair dryers is the mineral tourmaline, which is supposed to help reduce frizz. Even a piddly little wall-mounted hair dryer in a hotel one tester stayed at while writing this guide claimed to have it. The mineral is very pretty, but as our expert engineer said: “Tourmaline? Please, squared.” It’s impossible to see the tourmaline because it’s ground up and in the barrel of the dryer, and it doesn’t have to be present in very large amounts to be advertised on the box: Patents for gemstone dryers that we read involve a slew of minerals that manufacturers use to coat the inside of the dryer. Rebecca Kazin told us that she looked for tourmaline in a hair dryer but that there were no clinical studies on its being better for hair. Her exact words were: “I believe in tourmaline.” We read—in a patent—that heated tourmaline can emit electromagnetic radiation that can alter the structure of your hair. The person who holds that patent also has one for a device that diagnoses “body deficiencies” (the patent is not specific, but it does say you treat them with drugs) by measuring a patient’s electromagnetic field. Now is a good time to say that patents can give you a great idea of how something is supposed to work but are not necessarily fact-checked for scientific accuracy.

You definitely can ignore claims about “conditioning nano beads” or “silk proteins” that are, supposedly, infused in the heating elements and barrels of some dryers. “That is just marketing hype,” Romanowski said.