How to Perform a Strand Test for Hair Dye
Testing Colour on Hair for Henna, Indigo and Commercial Dyes
Jul 17, 2009
While boxed dyes should, in theory, turn your hair the colour on the box, the actual result can vary according to the original colour of the hair, previous dye jobs and hair damage. In addition, chemical hair dyes occasionally react badly with dyes from other brands, which can result in strange-coloured hair or even scalp burns.
When using henna to dye hair the final colour is variable according to the original hair colour, the length of time the henna is left on the head, any additives to the henna paste and the heat at which the henna sits. As with any strand test, it is important to keep as many variables constant as possible to get a true predictor of the final result. Time how long the dye stays on the strand, make a note of whether the hair is washed or unwashed to begin with, and keep the test strand close to your skin (a pocket is fine) to replicate body heat.
Harvesting Hair for a Strand Test
The easiest, quickest way to harvest hair is simply to snip off a lock. For people with uniformly-dyed hair, this is fine; but most natural heads of hair have great variations of colour, so a single lock might not accurately represent how the colour will take over the whole head. And of course, not everyone is happy to cut a lock out of their hair!
The alternative is to use shed hair. Shed hairs come from all over the head, so will generally give a representative sample of your hair’s highlights and lowlights.
To harvest shed hair, brush your detangled hair with a boar bristle brush. The bristles will catch loose hairs and collect them. After brushing, simply collect the hairs that have collected in the brush.
These hairs can simply be rolled into a matted ball for most dye tests. If the hair is two-toned due to a previous dye job that has partially grown out, it may be useful to arrange the hairs in a lock with all roots at the same end. This gives a truer picture of how the new dye will look on the hair. After arranging the hairs correctly, use superglue and a piece of tape to secure the lock at one end.
Performing the Strand Test on Hair
To perform the strand test, simply prepare and apply the dye to the hair according to the manufacturer’s directions. If you are performing multiple strand tests at once – for instance, to compare different henndigo mixes – keep careful notes of which strands are in which mixture. Keep a note of all other variables – heat, time, strength of dye and so on – and try to make the conditions as close to those you will use when dyeing your hair. A strand test soaked in henna for twenty minutes will not show you what hair soaked for two hours will look like!
After the Strand Test
Rinse out the dye, making sure you do this the same way as you plan to in the shower. Consider water temperature and any hair products used – oil treatments can pull out dye. Then leave your strands of hair for a few days. Henna and indigo require time to oxidise, which means their final colour will turn darker and richer a few days after dyeing. Henna and henndigo also change colour in the light, so be sure to inspect the hair in natural and artificial lights, including bright sunlight. Hold the lock up against your skin to see if it works well with your skin tones. If you plan to dye only part of your hair, hold the strand against your natural hair to see the contrast.
If you like what you see, you can dye your hair with confidence. If not, you have successfully avoided a hair disaster! Strand tests are particularly important for permanent dyes (especially henna, which is nearly impossible to remove); however, they can be useful even for semi-permanent or wash-out dyes. Some people find that supposedly temporary hair dyes stain their hair for good, so it’s worth testing these dyes on a lock to make sure it does indeed rinse out.
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