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How long does prepared dye last?

I’ve been working on a project that involves painting with dyes. I’m super excited about it! However, I followed Dharma Trading’s directions for painting with dye to a T, spent hours hand painting it, and when I washed it the color faded dramatically. These were supposed to be brilliantly purple flowers. Instead, I have these dusty, grayish bleh blues.

Black out lined dusky blue painted flowers around green watercolor paint
These were supposed to be vibrant purple!

Disappointed is an understatement. Despite knowing it took me hours to paint the first time, I want to re-dye it, but I don’t want to waste my time again until I know what will work.

Many of you probably don’t know that I was a scientist for a while.  Worked in a lab, complete with a snazzy white lab coat, super sexy safety goggles, latex gloves and sensible closed-toe shoes.

I’ve left the lab, but once it’s a part of your life you can never leave the scientific method behind! So today I merge my two worlds together to bring to you How Long Does Dye Last After Preparation? (or as I like to call it Now Why the Heck Isn’t That the Color I Wanted?)

Let’s Science!

The Questions

Before setting up an experiment, you need to have some questions you want answered. Wanting to paint with dyes without color loss is just a little too broad, so here were the specific questions I asked:

  • Is it better to add soda ash directly into the dye mixture or soak it into the fabric?
  • Does thickening the dye with sodium alginate make the dye less effective?
  • How long can I use a dye before it fades noticeably?

The setup

To start with, I have two pieces of the same cotton fabric. One just dry, normal fabric. One was soaked in soda ash solution then hung to dry overnight.

I mixed together some chemical water at a 1 Tbsp urea to 1 cup water ratio.

For each piece of fabric there are two dye preparations: one thickened and one just regular ‘ol dye. I actually used extra sodium alginate (2 tsp per cup – double what Dharma had recommended) because I really wanted to see if it was affecting the dyes.

The dyes for the dry fabric had the soda ash added directly to them (at a 1 tsp soda ash to 1 cup urea water ratio) while the soaked fabric did not.

I portioned off the exact same amount in a bunch of tiny cups (or large cups as I ran out of my tiny ones) and added recommended amount of dye for each.

Then I simply painted a splotch at various time points throughout the day.

Whew! That was a lot of sciencey stuff, but thanks for sticking with me so far! If that didn’t make much sense, here’s a picture of the setup that should make it a little easier to understand.

Rows of dye colors with two pieces of fabric, both with lines of colors painted in a row

The results:

This is always the most exciting part! What do you see?

Rows of results from dye test

These were my observations:

  • Soaking the fabric in soda ash first and letting it dry overnight saw no discernible color loss throughout the whole experiment!
Comparison of 0 hour and 12 hour dyes on soaked and dried fabric
Side by side comparison of 0 hour and 12 hour dyes on the soaked fabric
  • When the soda ash was added directly to the dyes, purple and yellow faded quickest, with purple being noticeably duller already after the first hour and yellow after the second. The rest weren’t too far behind and my green turned more teal by the end. By 12 hours everything was pretty pale.
Comparison of 0 hour and 12 hour on unsoaked fabric
Side by side comparison of 0 hour and 12 hour dyes on the unsoaked fabric. I’m sorry they don’t line up very well!
  • The unthickend dyes spread surprisingly differently on the two fabrics. On the unsoaked fabric, the dyes spread pretty evenly throughout the fabric, but on the soaked fabric the dyes spread with a more uneven edge.
Spread pattern of unthickened dye on untreated fabric
Spread pattern of unthickened dye on untreated fabric
Spread pattern of unthickened dye on treated fabric
Spread pattern of unthickened dye on treated fabric
  • The thickened dyes didn’t always fully penetrate through the backside of the fabric, leaving it look a little more blotchy. I doubt this matters much beyond the fact that your fabric will end up having a definite front and back side when you are done.
Paint blotches seen through backside of fabric
You can see some blotchiness through the backside of the fabric from the thickened dyes

In conclusion:

If you want bright, bold colors the clear winner was soaking the fabric in soda ash solution first and allowing it to dry. I’ve never been particularly speedy with my art, so I need to have time to work without worrying about fading colors. Thickening didn’t affect the color, so that’s going to be more of an artistic decision – clean lines or bleed effect?

I can only recommend adding soda ash directly to dye in very specific circumstances in which you are going to immediately (and I really do mean immediately) use all your dye. It just fades surprisingly fast.

I put together a post with recommendations for painting on fabric based on what I learned here today.

Did you have any interesting observations or comments on this experiment? I’d love to hear it! Comment below!

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March 3, 2021 5:31 pm

I know this was two years ago, but it’s super cool! Thanks for all the all the info, this will really help in all the dye art I’m going to do 😁

Last edited 3 years ago by KitKat
Veronica Russell
May 13, 2021 12:05 pm

Hi, I cannot easily find sodium alginate in my country, it has a very specific use in modern cooking and it is way too expensive. Do you know if I can use something else instead? Thanks!

TX Dyer
TX Dyer
September 1, 2023 8:06 pm

Thank goodness for Pinterest! You have saved me SO much time by documenting at least half of the Procion dye experiments I feel I need to do.