JanuaryNoir has been doing henna for quite some time now and her advice is very valuable to the community here so I will be for sure saying I second the fact that YOU DO NOT need lemon juice for dye release of henna. I personally have been doing henna for at least 10yrs. I have added a splash of lemon juice here and there but sometimes I just plain forget.
For best color results using fresh henna powder is essential. Like this year's crop (2007) or at least last years crop (2006) even though it is 2008 right now this year's crop is still 2007, as 2008 only comes out later in the year from summer to fall. You will see color results even on very dark hair using a good quality pure henna powder such as those labelled body art quality, and most popular right now for best color results wil be Indian henna powder.
PET I am not sure if you added conditoner into your henna paste mixture or not, but if you did you would be diluting the recipe too much, and the color results won't be as intense or noticeable. Another thing was the amount of water, I don't usually measure so make sure you don't add too much water but just enough to make it thick and muddy like a nice pancake batter.
Some people have done tests to show that honey does lighten the results of henna so if you don't mind that, then keep that in mind when using honey. It is known to be a natural hydrogen peroxide.
It is also best if using powder to not add any boiling liquid but add warm liquid up to mildly hot. Let the henna sit for a few hours and leave it for 4-6 hours or overnight if you'd like.
I agree moisturizing helps as well avoid any dryness and too much acid causes dryness as well.
PET your hair does look very shiny and beautiful!
Been missing all of you. Hope everyone is well and sorry haven't been around just been feeling a bit sick last few weeks. Just trying to keep up with the bare minimum.