Why should I not wash my hair before dying it?

They just don’t want you to wash your hair and then slap the color on. It gives your scalp and your hair a natural protective barrier. You don’t have to let it get filthy, just don’t hop right out of the shower and put the color on.

It is interesting that it suggests applying to “damp” hair. I’m not sure that I really understand why they would want you to do that…

It might help if you find a link to that exact hair dye ..and post it. Then others can see what you’re using.

I think the damp hair bit is leading folks astray. Some of them say that, others say to put it on dry hair. It’s not a problem to dampen my hair but they all say not newly washed.

The natural oils on your hair and scalp help protect your scalp from the strength of the dye. Dyes don’t go on any better if your hair is clean. Instead, just plan to dye your hair about an hour before you take your daily shower, and that way, you’ll get all the dirty goodness without having to go longer with dirty hair. After rinsing out all the dye throughly, and putting a good conditioner in, you really shouldn’t need to wash your hair as well – it should be clean.

So, does extra grease on the hair stop the dye from reaching it?

No. More like the extra grease stops the dye from cutting all the way through the hair and breaking it off – hair dye is powerful stuff, like bleach, and you have to account for that.

The oil on your hair just acts like a natural barrier. It can also help for the color to adhere better, by filling in the gaps where your hair may be porous from previous damage.

Me, the greasy hair and the box of hair dye will give it a go tonight. I’ll report back!

Because the instructions say so.

when I dye my hair I always apply it to dry hair and let it process for 45minutes before washing it. I think the reason they don’t want you to put it on wet hair is because the color won’t saturate.

I think its because your pores are more likely to be open after washing your scalp and so you risk dye being absorbed by your scalp more.
Also it could be that your hair strands are won’t be dry enough inside to absorb the hair dye as well.
I usually wash my hair the day before and give it at least 24 hours to dry properly. I also use a Vo5 because it helps strip the hair clean without leaving any residue on it.
Don’t use any hair conditioner either because it will also effect the results of your dye. The greasier your scalp the less likely your hairdye will last on your roots. So try not to do anything that will cause too much sweating before you dye.

You’ll never guess what. My hair looks fine this morning because I have dyed it and washed it. Yes, all this angst was for nothing as the instruction leaflet said to dye then rinse my hair then wash it before putting on the conditioner. Very strange – I’ve never had that before. It was a supermarket brand. The colour seems to have taken well, despite the grease and my scalp was not irritated either. It went on to dry hair this time. Thanks guys!