How Many Microns is a Coffee Filter?

A paper coffee filter with coffee in it.

I have to be perfectly honest. I didn't know a micron had anything to do with a coffee filter until the other morning I was having coffee with my neighbor Smith Willis. Smith, who many years ago taught entomology at Louisiana State University, has a little knowledge of just about everything under the sun.

Smith was sipping his cup of Joe in my kitchen and looking admiringly at the pot of coffee behind me when, out of the blue, he says: “I bet you didn't know, neighbor, that a coffee filter is 20 microns.”

“Twenty microns?” I smiled. “That's interesting, Smith. I would have never guessed.”

Microns? I didn't know what my 86-year-old friend was talking about, but I played a long with him and asked, “You are certain about that, Smith? A coffee filter is 20 microns?”

“IT'S IN THE NEIGHBORHOOD OF 20 MICRONS, BUT CAN DEVIATE IN TRUE PORE SIZE.”
He took another sip of coffee, looked at me, and said,”Well, neighbor, the normal filtration size of a coffee filter is in the neighborhood of 20 microns, but coffee filters are not made to an exact criterion. So, some are likely to deviate in the true pore size.”

I got up and walked around the table a couple of times and went to the pot of hot coffee and poured myself another cup. I like mine black.

“How about it, Smith? Would you like some more? Can I heat you up?”

“Sure, neighbor,” he said. “You know how to make fine coffee.”

“Must be the microns,” I said, and watched him doctor his cup with cream and sugar.

“You’re funny, old buddy,” he said. “Microns. You make it sound like microns are something you serve with coffee.”

“I guess I did at that,” I grinned.

He looked into his coffee and looked up and said,”I guess you are aware, neighbor, a single micron is not a lot.”

I ACTED AS THOUGH I WAS WELL-VERSED ON THE SUBJECT OF MICRONS
I didn't know what he was talking about, but acted as though I was well-versed in microns and finally said, “Yeah, Smith, I'm certain no self-respecting coffee filter would be seen without a micron or more”

“Twenty to be precise,” Smith said. “Twenty at least.”

“Well, Smith,” I said. “Coffee wouldn't be coffee without a good 20-micron filter in the pot. Would it, Smith?”

He looked at me and grinned, “You amaze me, neighbor.”

“And you amaze me, you geezer,” I said. “You know so much about everything. How do you do it.”

He took another sip of his coffee and said, “I read a lot, neighbor. I read a lot.”

I told Smith that I had been reading a lot lately also. That I was rediscovering Ernest Hemingway and John Steinbeck.

“Hemingway is good,” Smith said, “but my favorite has always been Steinbeck.”

“I like Steinbeck, but he was wrong about one thing, Smith.”

“Wrong about what, neighbor?”

“I SAY THERE IS NOTHING IN THE WORLD LIKE THE FIRST TASTE OF COFFEE.”
“Well, Steinbeck said there was nothing in the world like the first taste of beer. I say there’s nothing in the world like the first taste of a good cup of coffee. What do you think, Smith? (https://www.azquotes.com/quote/555199)

“I think your right, neighbor. There’s nothing better than the first taste of coffee. But I wasn’t aware that Steinbeck had said that about beer.”

“Well,” I said, “Steinbeck may not have actually said that. One of his characters, I know, said it in one of his novels.”

My neighbor stood up and helped himself to another cup of coffee. His third of the morning.

“Steinbeck was a great writer,” Smith said as he poured coffee into his cup, “but apparently he never tasted a good cup of coffee.” He sat down again.

“You never know,” I said. “Steinbeck had a lot of wisdom. He might have even known a coffee filter is 20 microns. I’m sure he drank a few cups of coffee in his time. He knew a lot about the Bible, he knew a lot about marine biology. I’m certain he knew how to make good coffee.”

Smith took a sip of coffee, looked up at me and said, “Coffee filters are interesting? Don’t you think, neighbor?”

I TOLD MY NEIGHBOR I WAS MORE INTO SPORTS AND MUSIC, NOT COFFEE FILTERS
“I don’t think much about coffee filters, Smith. I’m more into sports and music. Baseball and football and Willie and Merle. What’s so interesting about a coffee filter?”

“Did you ever think of what you would do if you didn’t have a coffee filter? Could you still make a good pot of coffee?”

“Hell’s bells, Smith,” I shot back at my neighbor. “I could always use a paper towel for a filter. Everybody knows that!”

My neighbor laughed and reminded me that when a paper towel is used as a coffee filter, that the towel will many times come apart and leave a lot grounds in the coffee.

“You would have to remove the grounds from the coffee before you drink it. You wouldn’t want to do that, my friend. Don’t you know also that the paper towel has chemicals in it and the chemicals can leak into your coffee and ruin the taste.”

I told him I has never thought of that.

“Yes, neighbor,” Smith said, “the coffee filter should not be taken lightly. As we have already said, the typical filter is composed of filaments 20 microns wide.”

“Filaments? Did you say, filaments?”

“Yes, filaments, neighbor. You know what filaments are, neighbor. Very fine threads or threadlike structures. Some folk call them fibers or fibrils.” (https://www.dictionary.com/browse/filament).

“Of course. Filaments,” I said.

Smith continued and said filaments allow particles that are about 10 to 15 microns to move through the coffee filter.

“YEAH, THE COFFEE FILTER IS STILL 20 MICRONS. THAT NEVER CHANGES.”.”
“That is interesting, Smith,” I told him. “I would have never guessed. But we’re still talking about the same 20-micron filter. Am I right?”

He laughed. “Yeah, the coffee filter is still 20 microns, neighbor. That never changes.”

“Well. I think I understand a little more, Smith. We’re talking about thickness, right? A coffee filter is basically only 20 microns in thickness.”

“That’s it, old buddy,” he said. “You're getting it now. Do you want me to put that in some sort of perspective for you? What about copy paper. Copy paper is how many microns you think?

I told him I had no idea. Only that copy paper was thicker than a coffee filter, a paper towel and probably toilet paper.

“Copy paper is about 100 microns, they say.” Smith replied. “ It’s much thicker. Copy paper would make a terrible coffee filter.”

“I was just thinking about Steinbeck, Smith. The coffee filter probably wasn’t even invented back in the ‘30s when Steinbeck was writing Grapes of Wrath. His coffee, I’m sure, did not taste as good as the coffee we’re drinking this morning.”

“Why don’t we ‘Google’ it, neighbor? Smith asked. “Your laptop is right here in front of us.” He got up and poured himself another cup of coffee. The pot was neatly empty and I told him turn the maker off and he did.

“Good coffee,” he sighed. He sat down and soon had cream and sugar in the cup.

I asked Smith what he wanted to “Google” and he said he had completely forgotten what we had been talking about. He sipped his coffee and seemed to be in deep thought.

“We were talking about the coffee filter, you geezer. Filaments, copy paper, paper towels, filters 20 microns thick, Steinbeck and the whole nine yards.”

HISTORY OF COFFEE FILTER REVEALS GERMAN HOUSEWIFE WAS THE INVENTOR
“Sure, neighbor, we were wondering if coffee filters were around when Steinbeck wrote his great epic back in the '30s. Go on. Google it. The history of the coffee filter.”

I pulled it up and read out loud to Smith that Melitta Bentz, a German housewife, had invented the coffee filter.

“Guess when it was invented, Smith. You’ll never guess.”

“Tell me neighbor.”

“Well, it says here that in 1908, Melitta patented the paper coffee filter and started the Melitta Bentz Company with her husband. Demand for the new filters were overwhelming and Melitta went on to gain awards for her invention.”

“Interesting,” Smith said. “So, Steinbeck would have had access to coffee filters back in the '30s. Maybe he did make a good cup of coffee.”

“I wonder if Melitta's filters were 20 microns, Smith? What do you think?”

“I don't know. Doesn't it tell us there?

“No, it just says Melitta used a sheet of blotting paper from her son's school notebook to make the first coffee filter. She poked holes in the bottom of a brass cup, using nails, and then lined it with the blotting paper before filling it with coffee.”

“Clever,” Smith said. “She was quite clever.”

“Well, Smith, I have learned a lot this morning about the coffee filter. I don’t know if I”ll ever be able to use this information. But you never know.“

“You never know,” he said. “I guess I'll move along, neighbor. Have a good day.”

Smith hobbled out the back door and was gone.

My wife then entered the kitchen and I told her Smith had just left.

“He drank all the coffee, too,” I said.

“So what have you great minds been talking about this morning?”

“We've been talking about coffee, coffee filters, paper towels, John Steinbeck, filaments, microns and the whole nine yards.”

I laughed and asked, “Alice, do you know how many microns is a coffee filter?

“Sure do,” Alice said. “A coffee filter is 20 microns.”

“Why that's right,” I said. “How in the world did you know?”

She grinned and said softly, “Twas Easy, honey. I've been just outside the door, listening to you all morning.”

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