Basically this

Sort by fabric weight and “toughness” not the other ideas.

You want jeans with towels and rags and socks and goonch together. Thinner shirts and blouses with thinner slacks together. Heavy jumpers and aprons and work pantaloons. Always cold water, lay flat dry unless you find that too annoying and time consuming (I personally prefer air dry but it’s probably me being a bit fussy and too frugal buy hey free winter home humidity too)

edit: Oh and you must inside-out the good items. So the nice exterior doesn’t get beaten to rat-shit and all pilled up. Let that rubbing-rubbing-rubbing damage to the fibers happen on the interior of the garment which nobody sees

Generally, after two or three washes, you don’t need to separate any more. You really only get bleeding with new fabrics, and even then only with cheap fabrics. As an example, if you order Amazon’s cheapest towels, not only wash them separately, wash them before you use them unless you want the color on you. But even those eventually stop bleeding.

If you’re going to sort, the way I was taught is to separate colors from whites, with blacks being a separate load as well. The idea is that the bleed from any of the colors isn’t going to be enough to matter since there’s already dye present, which means there’s less ability to take on new dye. That can fail, and you end up with the color of things changed. So you still always test any new fabrics before throwing them in with other colors. But, generally speaking, if you don’t have the time, don’t have enough of that color to make a load, or just don’t care about color change, the risk of any color change being huge is low nowadays.

The only reason to do blacks on their own is that it mutes other colors when it bleeds.

If you’re really paranoid about it, either do each color on their own, or make batches where the colors bleeding wont be as significant. Like, blues and greens, or greens and yellows. Any bleed that does happen like that won’t be as noticeable, if it is at all.

But I never saw in all my years washing other people’s clothes anyone that had enough of every color to make multiple loads without waiting way too long between washings. Maybe in a really big family you’d pile up enough mixed colors in a week or two to make full loads of multiple single colors, or even two colors.

You’re also usually okay washing bed sheets and clothes together, though you can pull out stuff with zippers and metal buttons if you take want to maximize life spans of the rest. Being real though, making a load of those together is just going to shift which items get the teeny, tiny extra bit of wear from the fasteners. It might be worth it with heavy denim, but I wouldn’t and don’t bother personally.

Now, as far as types of fabric, you run into some issues. Good wool might need its own special care, but you’d want to refer to the label to determine that. Silk is hand wash only unless you like ruining silk. Cotton, linen, polyester, rayon, and nylon can all be washed with any other fabrics, no issues. At worst, you might run into a little extra pilling with the natural fabrics being washed together, but I’ve sever seen it actually happen more than what the fabrics do on their own just from being washed.

You specified merino wool. Afaik, you should machine wash as the default. But wash in cold only, and go with the bare minimum of detergent. Make sure you pull it out as soon as possible to reduce wrinkling, and hang to dry. Yeah, in theory your can machine dry merino, but if you’re asking this at all, you want to maximize the life and appearance of your clothes, so hang to dry.

Hand washing works as well as you’re willing to put in the work on, but wool tends to hold on to oils and sweat residue more than most fabrics, so you have to really work at it compared to something like cotton that gives up oils as easily as any natural fabric will.

If you’re having a problem with lint on your laundry, do your towels and other terry fabrics on their own. Most of the time, that’s where excessive lint is coming from. But if you aren’t having that issue, don’t worry about it.

A lot of separating of types of fabric goods, like sheets from clothes, isn’t about what they’ll do to each other or needing different types of care, it’s about convenience. Folding and storing sheets all at once is easier than dealing with a mixed load, as an example. You do benefit in being able to run things like towels hotter than you’d want with most clothing, but it’s a marginal benefit imo.

My laundry isn’t sorted much at all unless I get new stuff. Towels and washcloths and the like stay in their own loads. Clothes together, with only a few extra heavy fabrics on their own (like my canvas outdoors stuff and gis). Bed linens tend to be a load of their own since there’s two beds worth of those at a time, there’s just not room for more. But, when that’s not the case, I tend to throw them in with towels.

And, as always, check your labels. While it isn’t a guarantee, the recommended care on them really is the best pick. You’ll run into some chinese fabrics where it’s just generic instructions, but those tend to default to the least wear options anyway, so it won’t hurt anything, it just isn’t ideal. The companies using outsourced labor still specify the label contents, so it’s only when it isn’t a brand at all that you see the generic labels.

I also tend to recommend that you avoid fabric softener. They really don’t do anything useful, they cost extra, and a lot of people are sensitive to them and don’t realize it. If you’re getting itchy a lot, and you’re using them, try a few weeks without. Same with rashes where the fabric is extra close to skin.

Everything together in cold water

Slap them all in the washer together and enjoy any new coloured clothes I have.

You’re completely overthinking it. I keep white separate. Colors get their own basket. Denim goes in a separate piles after it really smells (it honestly shouldn’t be washed very much). Towels get their own load due to shedding. Sheets sometimes go in with the colors.

I do everything on cold. I use the plainest of plain detergent. If there’s a smell in polyester or nylon clothes I’ll put in some Clorox 2.

Dryer on low or medium until mostly dry. I’ve got a fancy one with a moisture sensor that actually works so I let that determine how long. Usually 25-30 minutes.

Citation: https://www.nytimes.com/wirecutter/reviews/wirecutter-show-podcast-20240821-better-laundry-secret/

Most damage comes from heat, and rough handling, so I sort by structure/weight, and wash almost everything on cold, and tumble dry on low, auto-sense.

The only color I wash separate is white so it can run hot and with bleach.

I also presort, by weight into 4 bins heavyweight, middleweight, lightweight/dress-shirts, and finally undergarments/delicates/socks

We might go a 2-3 weeks between a running a particular bin so we can separate things out just because there is enough to fill out it’s own load.

Undergarments and deli sites go together, might add leggings or lightweight tops to fill out a load

Socks are separate merely because we like fluffy wool socks and they will fill their own load, and it’s easier to pair them when they all come out together. Otherwise they’d be with undergarments. Might run on warm if the foot stank is real bad.

Sturdy fabrics like denim and duck all go together in a denim cycle it’s just cold/cold with a heavy spin

Sweats and other heavy bulkys go together so they don’t twist up lighter clothes. Might run these with denim or towels

Lightweight tops and button down shirts go together. Lightweight sweaters might be get mixed in too.

Then general laundry is middleweight fabrics: t-shirts, slacks leggings, etc.

If there’s enough for their own load, towels get a hot cycle to get cut down on microbial growth. Otherwise they go with denim and/or sweats. NEVER USE FABRIC SOFTENER/DRYER SHEETS ON TOWELS. It makes things softer by adding oils THAT prevent them from absorbing water, which is the whole point of towels.

Sheets and pillowcases might get a warm cycle and pre wash to help cut through accumulated body grease, etc.

I don’t separate colours, only new clothes I put in with towels, sheets or clothes that I wouldn’t care if colour bled.

I never wash with hot water, only warm or cold. Low heat dry and cold water washing is really the best effort-for-performance to get your clothes to last, you can hang dry some of them but I personally can’t be arsed.

Easy. I only have black clothes. If there’s bleeding, I can’t see it.

I have hot wash for towels and bed stuff. Cold for literally everything else. I’ve never had anything bleed, even new stuff.

I try to wash whites alone, but that’s it, and even then I’m not super strict about it. It helps though that probably 90% of my clothes were thrifted, bleeding is mostly a problem with brand-new fabrics

We don’t, we separate into bulky clothes (sweats, jeans, heavy shirts), everything else, and delicates. We wash with only cold water (modern machines and detergents don’t need hot water and it won’t get things any more clean, it just wastes energy). Bulky goes in first, then normal, then delicates. I’ve done this for at least 10 years with zero issues across a variety of machines and water hardnesses.

I separate by the kind of detergent and cycle a thing is run on.

Gym/sleep t-shirts, denim, towels all get a hot wash with oxi-clean and fabric softener because I love the smell come at me bro.

Elastics - things that are mostly elastic/spandex/polyester - socks, underwear, leggings, sports bras. They get a hot/cold wash with a pre soak and extra rinse. The they get the free and clear detergent that washes cleanest and leaves no smell.

Daily wear/delicates - gentle cold wash with woolite with low tumble dry or hang dry. I only ever have like 4 of these with each wash. Generally the nice, more expensive stuff I wear in public that I want to last a long time.

I don’t care what color anything is.

I put whites into one pile, which allows me to use bleach if I want. The rest I split into “rough” or “heavy” fabrics (think jeans) and more “gentle” fabrics (think slacks). I’m not worried about the colors so much as wear on the clothes that can’t take a beating by getting mixed.

Ive seen clothes bleed like twice, once was a set of dark sheets I washed for the first time, which bled a shitload, and the other was a cheap promotional shirt I bleached which turned the water black.