How to lighten hair with lemon juice?

I know you have to be in the sun but for how long? I have dirty blonde hair now and I'm just looking to get a few natural highlights. How much juice should I put in my hair? Is it OK to put my hair in a messy bun while outside or will it make it uneven and have weird patterns?How to lighten hair with lemon juice?
I have light brown hair and I use lemon sun-in sometimes. Gives me some natural highlights and you can't really notice when the roots grow in (unless you lighten it a lot).

If you don't want to buy sun-in, which is around five bucks a bottle, then get some lemon juice and mix it with a bit of water, and maybe some peroxide. shake it up in a spray bottle. I only do the top layer of my hair... Just spray it on, starting at the roots, and evenly distribute it with a comb. Works best if your hair is a little damp.

You'll notice after spending a day in the sun that your hair is a bit lighter, keep doing it till you're satisfied with your hair colour.How to lighten hair with lemon juice?
have your hair straight when you do it.. not in a messy bun (like you said ';it 'will' make it uneven and have weird patterns'.. have your hair be dry also, not wet like you just got out of the shower or something. put on a fairly good amount evenly over 'the top' layer of your hair. so that it makes the top of your hair seem moist! then lay out for about an hour (or more if wished). this will ensure the best results(:
you have to saty in the sun until you start to see changes, just spray the juice evenly like hairspray, i don't think you should put your hair in a bun, just leave it down.