I just did this last weekend and I don't know why I didn't think of it before: strand testing hair products.
How I did it:
I wanted to test 3 different gels over Back to Basics Pomegranate Conditioner. For me, this is a process that would normally take up to 21 days, since I only fully wash and condition my hair every 6-7 days. If I do cave in and wash it [even co-wash] more frequently, it gets very dried out and flyaway.
I was really keen on minimizing my time invested in this, since gels haven't worked very well for me in the past. I just wanted to get in and get out. After doing other product testing the last month or so and winding up putting my hair up 95% of the time because of poor results, I thought there had to be a better way.
So last weekend before I fully washed my hair, I just washed a section of it, used the products I wanted to test and pulled the rest back into a ponytail. It didn't even look really that weird, I just had some sections around my face hanging loose. When I needed to go out I tucked them under a pretty scarf, tied loosely. I got to see how they were after 12, 24, 36 hours.
Result: in a day and a half [and not one bad hair day] I figured out that BRHG is going to work way better over Abba Weightless and Devacurl Angel
I also got to compare the results side by side, in the same weather conditions
, which was invaluable.