Permanent hair dye washing out

[SauvignonBlanketyBlank]

I dye my hair at home using box dyes every 6 weeks or so.I use black hair dye and it washes out around the hair line quite quickly.Is there anything I can do to prevent this?

Do you always use the same brand ?

Some are bound to be better than others .

Do you start with the roots so that has the longest contact time then do the lengths are are being over-dyed ?

And one tip I found , which works really well. After you dye don;t wash your hair for 3 days ( of course make sure your final rinse has cleared the residue otherwise it might irritate your scalp ) .

And a final cold water rinse - (supposed to 'close' the cuticles on hair , not sure if that is balony though )

Oh , and Colour Shampoo (ie shampoo for coloured hair ) does help .

No dandruff shampoo though - strips colour . (I've done the VitC + dandruff shampoo treatment . It does !)

My semi is flowing out of my hair from the look of the water - it's been red every day since colouring it. It's starting to look crap and only been done a week so no advice but my sympathies. Was thinking I may get a toner to try

I'll try the not washing hair thing.I use different brands so god knows what the problem is.

I honestly think that some people's hair just doesn't retain colour very well. When I box dyed mine a dark colour, it kept washing out within a few weeks.
I've now gone lighter to hopefully cover the greys for longer. Downside is paying a salon for highlights though, rather than getting a cheapy box dye