Get all of the above ingredients ready. You will need to do a strand test first with some hair from a brush.
Boil 12-16 oz. distilled water.
Add the hot water to the henna slowly, stirring with a non-metal spoon. Do not add all the water at once. Check the consistency as you stir. It should be fairly thick and creamy. When you lift the spoon out of the mix, it should cling to the spoon. I usually only use about 12 oz. of the water.
Depending upon the color you choose, it will need to cure anywhere from 10 minutes to 3 hours. Light Mountain suggests you cure the red henna for 1-3 hours, but I have applied it after 20 minutes and it has turned out fine. If you use the neutral, it doesn't need to cure and you can use it right away.
Remove all jewelry. Metal and henna are not good together.
Cover your floor, counter, etc. with newspaper.
Wrap your old towel around your shoulders, and pin with a safety pin.
Divide your hair into sections and use barrettes or hair clips for easier application. Even though I mentioned that metal should be avoided, I use metal barrettes for this. I just make sure to not have any henna touch the barrettes. I remove each barrette as I go.
After putting on the included plastic gloves, start applying the henna from the bottom and work your way up the scalp.
After covering all your hair, put the included plastic bag on your head and cinch with a clothespin.
Leave the henna on for 45 minutes up to 4 hours. I usually leave it on for 45 minutes to 1 hour. Use intermittent heat for 5-10 minutes to help set the hair. To be honest, this is the first time I actually did this step. Normally I haven't and it has turned out just fine. The heat is supposed to bring out more enhanced red tones. If you are using red, auburn, mahogany, or light brown you may want to include this step. Just be careful not to melt the plastic bag-cap.
Rinse with warm water. Light Mountain Henna says to aid in removing the mixture, apply conditioner to the hair, then rinse again. They also say to wait 24 hours before shampooing. However, I have used shampoo twice during the removal then conditioner, and not only has it turned out fine, it has lasted 4-6 weeks. This time I only rinsed because the consistency of the henna was really creamy. There were times when the mixture has been a bit gritty. It just depends upon the batch you get. If you get a gritty batch, don't let it deter you, it will still come out. Of course, a creamy batch is preferred, and if you stick with it, you will get many of those.