I have very old GHDs and although they still do the job and eventually curl and straighten my hair, they seem to be dragging through instead of slipping through my hair. I'm getting obvious lines when I curl.
My coriolis mini ones have never done that, but they're much newer and have shiny silver plates rather than the orange GHD plates, but curls are smaller though.
I always put serum on my hair and it works fine when I use the coriolis but not GHDs, any tips?