Dull question about washing powder/liquids

[SkepticalCat]

What is best to use for black clothes - washing powder formulated for colours or liquid (and bio or non-bio liquid)?

I have been using colours washing powder (I think Persil, and more recently Aldi own version) to wash school uniform which is black. I noticed it getting quite faded towards the end of the year, so would liquid be better? Or would it not make any difference if colours washing powder (presumably) doesn't contain bleaching agents, unlike washing powder formulated for whites?

I have always found powder to be harsher than liquid.

I’ve been using Aldi’s powder for years as I prefer it to anything else. I use the one for colours and white’s depending on what’s in store. I do a black wash each week and have done for years and never noticed any fading. My son’s school polo shirt faded after the third wash but everyone else’s did too so I’m putting that down to the quality of the product. You can always run the faded clothes in the machine with a Dylon dye to freshen them up.

Thank you. Think I'll continue with Aldi colours then (I also use their one for whites as well).

Good idea @CatsMother66 to put Dylon in the machine to freshen up.

Surf have a detergent for dark washes it smells really nice too

@SkepticalCat, it’s a brilliant idea to use the dylon dye isn’t it? It’s not my idea though, my friend does it to freshen up faded jeans or tired towels. I wish I had thought of it years ago before I’ve got rid of tired looking favourite clothes.

It's the bleach in biological washing powder that's activated by a hot wash so cool temp and turn them inside out before you was them.

I use colour powder as it's a cardboard container rather than plastic and i think liquids can clog the machine