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How to do a Strand Test

Published on 20th March 2010

Will bleaching another time damage your hair? Will one colour look okay dyed over another? You just don’t know until you try. But dyeing your entire head of hair only to find out that second bleaching was more than your hair could handle and it has now all broken off or that dyeing red over your faded green turned your hair brown is really not ideal.

If you’re in any doubt about how a process or colour is going to affect your hair you should first do a strand test. Here’s how to do one:

Step 1: Collect the strand
Grab a few strand of hair at the back of your head where no one will see it. Move the rest of your hair away and snip the strands as close to your scalp as possible. 10 hairs should be enough. Don’t worry, you won’t even notice it’s gone.
You can do the strand test without snipping the hair but you’ll need to choose a strand in a place where you’ll be able to find it again and if you need to do more than one process (e.g. bleaching and then colouring) you may find it difficult to select the same hairs twice.
Always do a sensitivity test before letting the product come in contact with your skin.

Step 2: Secure the Hairs
For your strand test to be effective you need to keep the hairs in a neat bunch as they were cut. For this I use a small dab of superglue (any glue that isn’t water soluble will do) a few cm down the strand. Superglue is good because it dries almost instantly and does not wash off or dissolve easily. Alternatively you can wind some thread around the hair, tying it tightly several times.
Obviously you do not want to use superglue on hair that is still attached to you and, as always, follow the manufacturer’s instructions to avoid sticking your fingers together. You can skip this step if you have chosen not to cut your hair strand.

Step 3: Prepare the Product
Mix up the product you’re testing in the same ratios as you would for a full application. So if your bleach requires 30ml of powder to 60ml of peroxide mix in the same ratio of 1 part powder to 2 parts peroxide. You might find it easier to use 3ml of powder and 6ml of peroxide. Only a small amount is needed for your strand.
If mixing up a new colour, mix in the same quantities as you intend to use.
If no mixing is required, it’s a good idea to get a mixing bowl and brush ready at this step in preparation for the next stage.
Don’t forget to wear gloves!

Step 4: Check the Time
As with any test, accuracy is important. Check the time now as you’ll need to know how long to leave the product on your hair strand.

Step 5: Apply the Product
Apply the product to your strand test as you would to the rest of your hair. If using bleach remember that the hair that was closest to the roots will not process more quickly as it would if the hair was still attached to your head. This is due to a lack of heat from your scalp.

Step 6: Cover the Strand
It’s a good idea to cover your strand in plastic wrap, or leave it sitting in the product. The main point is that you don’t let your sample hair strand to dry out.

Step 7: Processing
If the product you’re testing requires the use of heat, now is the time to apply heat to your strand test. You can do this best with a hairdryer.

For bleaching, you should check your strand test by rubbing off some of the bleach from the hair every 5-10 minutes to check how much the hair has lightened. Timing is important so make sure you note how long the bleach has been processing at each stage. After checking reapply bleach and re-cover the hair strand.

For checking a hair colour, allow the dye to process on the strand for as long as you intend to leave the colour on your hair. This will give you the most accurate idea of how deep the colour will go.

Step 8: Lather, Rinse, Repeat if Desired
Finally rinse off the dye or shampoo out any chemical products like bleach or relaxer.

Step 9: Air Dry
Let your strand test dry naturally to give a true representation of the final condition of the hair. If you usually condition your hair you may want to condition the strand test after checking how it looks and feels dry.

Step 10: Compare
Now your strand has been put through all the stages above it’s time to check it against your own hair. Does it feel as soft and smooth? Is the colour the shade you had hoped? Do individual hairs return to the same size after being stretched? This is a good indication of condition. Damaged hair remains stretched and out of shape once pulled.

Although a strand test can’t give you a guarantee your hair will behave in the same way, it can save you from making some hair disasters.

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  • If your hair has an uneven tone or patchy dye job a few strand tests may be needed.
  • Avoid using hair collected from a hairbrush for a strand test as the results will be less accurate.
  • Any product you have to mix will go off after an hour or two so only mix a small amount for testing.