this is why we scour and mordant

UPDATED Oct 7/20

Oh, but it’s a pretty colour anyways.

Well, i can always overdye it.

But it was/looked clean when i bought it to dye.

It doesn’t matter, my clients like this colour.

But Famous Author *always* does this.

I don’t wash these anyways.

Did too scour: I washed this with my socks, before i dyed it.

Vinegar is too a mordant, you freak.

You’re just jealous i got dye from strawberries, ______, _______ and _____. (Insert appropriate inappropriate plant material here.) (This is usually said when said player has it explained to them, that even mordanting will not “fix” fugitive dyes.)


Here’s why you should scour, and pre mordant. Left to right: unwashed cotton, dye didn’t penetrate completely, many white spots visible, stiff as a f*****g board. Next, scoured only (soft as a baby’s butt!!!), no mordant, some colour uptake. Last, scoured and premordanted, deeper colour uptake. All were dyed in same pot of quebracho rojo, at the same time.


And please “but the colour is so pretty anyways” is not a good way to dye: the colours on the unscoured and unmordanted especially will/did wash out and will continue to do so, the scoured only will lose most of its colour with each subsequent wash, while the scoured and mordanted piece will keep its colour. And even “new” fibres that look clean need scouring.

Below cotton also, left scoured and mordanted, right scoured but no mordant.




A perfect example of what happens if you don’t scour properly, lesson learned in June last year:

I thought i had done enough on a new thread, but when i put them in tannin, this happened:

GREEN?????? I contacted Maiwa, my trusted supplier, and asked if perhaps it had been the soda ash in the initial scouring that had reacted (maybe not rinsed enough), as gallnut is a clear tannin, and stays to the “browner” tones after being used and stored. Nope.

Hi Arlee,

This is rare but it does happen, but it is not from the soda ash. Fabrics are often pretreated and contain substances which can leach out or react with the mordant. When used on it’s own Maiwa’s gallnut extract is usually a clear/colourless tannin. I would suggest trying other cotton fibres from different sources and comparing the results.


I had to REALLY scour again, properly, to get the green out of the threads! And it’s not that these were second hand or cheap threads–they were brand new, brand name, tightly plastic packaged and tightly boxed for shipment. Subsequent threads scouring has given baths of brown, yellow and absurdly, PINK. SCOUR YOUR THREADS TOO! Don’t skimp on this step. Even “PFD” (prepared for dyeing) fabric in MY opinion should be scoured—a. it’s been “prepared” for synthetic dyes, and b. you don’t know how much it’s been dragged over warehouse floors, handled, packed or shipped. (MMM, someone had tacos for lunch and wiped their fingers on the silk. SHARESIES!)

After scouring, I mordant EVERYTHING, according to fibre type. I *know* substantive dyes like indigo and walnut don’t require mordanting, but given that i use a lot of dyes that do need it, i’d rather have everything pre-done in case i grab the wrong chunk. Pre mordanting will not hurt substantive dyes. Some may be stripped out by a chemical indigo vat, but you should mordant again after indigo if you are going to overdye with another natural dye.

EDIT: Oct 7/20 Here’s another object lesson from my Dye Dungeon. I bought brand new white cotton velveteen, and lazily scoured it only once, and for only 45 minutes. I hung it to dry, and in the morning, THIS was on the floor:

I don’t know what textile additive this was, but i suspect because of the oil like iridiscent sheen it was a solvent, or other petroleum based product, something that is definitely not coming out easily, and that would certainly inhibit the uptake of mordants and dyes. I had wondered why the fabric took up very little dye:

This “should” have been a deep rich colour, as it had been properly premordanted according to fibretype.

So i threw it back in a big pot, and as soon as it started boiling (above photo), i knew there was still a lot of crud in it. At the end of the first hour long boil up, it looked like i was using a walnut dyebath–it was that dark and disgusting! It took 2 more boils at 45 minutes each, each successive pot with 2 heaping tablespoons of Borax, 2 of soda ash and some neutral soap, to get the water clear. (J.Liles recommends some fabrics be boiled up to 4 hours!)

There must have been a hell of a lot of fibre additives, because the snow white fabric i initially started with is now a lovely CREAM. That’s okay though, still a good base colour, and significantly, the plushness is softer and thicker feeling, probably due to shrinkage. (Be aware that scouring can shrink things as well, and better to know *before* you make plans than after and have lost 2-15% length or width!) Note too, the cleaning aspect i used is for CELLULOSE only. Soda ash will destroy proteins, and i doubt Borax is good for them either.

While we all know (or should if you do a little research) is that textile manufacturing is loaded with chemicals, whether it’s naturals or synthetics. Not all are done in one dedicated plant that does “only” synthetics, “only” naturals, and i suspect few that are “ONLY” “organic”. (Fact in case, that cotton lace in the first photo, had some suspiciously plastic filaments stuck in it, meaning the factory had produced synthetic laces as well, either on the same machine before, or near by on another run.) Some of the chemicals are cleaners, some are part OF the fabric, some are added after to give weight, sheen, dyeability and effect, and a lot of them ARE in our natural fibres, whether you think them clean or not. LINK> This will tell you how many additives and processes are used, most of the time. I remember when i was a young teenager, some fabrics *smelled REALLY weird”—turns out it was formaldehyde! I have friends who still can’t go in fabric stores because of their health conditions and all these chemicals.


HOW to scour? Maiwa: NOTE: different scour methods for cellulose vs protein fibres.  I use neutral soap and soda ash, or neutral soap and borax, or just neutral soap, depending on what i have handy, and depending on the fibre type.

HOW to mordant? Maiwa: I sometimes add a tannin step to protein fibres, not because they need it, but because they will extend the colour possibilities.

Yes, they are the same link. Maiwa has the BEST, FREE information available that is accurate, researched and trustworthy. Save the link, print it, share it, USE it.



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