Twirly Curls dolls have greasy hair

My blonde Twirly Curls Barbie wears her original bodysuit, skirt and shoes.
The Hispanic Twirly Curls has on 4811 Curtain's Up from 1984.

I've noticed that a lot of the early 1980s Barbies and friends have long greasy hair.  I always figured it was a defect in the plastic that was used and the plastic was leaking, much like the 1961 bubblecut Barbies and their oily faces.
After I played with some 1983 Twirly Curl Barbies' hair, I realized that it wasn't a defect--it's supposed to be that way.
I have had a number of Twirly Curls blonde Barbies, but I have only one that I bought in the box, and that is the Hispanic version.  In the box, the doll came with a purple chair with a suction cup on the bottom and the curling device.

The curler has two settings, I and II.

You need to sit Barbie in the chair.  First, bend her legs, then slide her in sideways.  You can't just plop her down in the chair--she won't fit that way.  Secure the chair to a table in front of you--you need the chair to be still.  An extra instruction sheet indicates that you might want to dampen the suction cup to adhere it.  Then turn Barbie around so that you are looking at her the back of her head.
There are two steps to the curling, and the curler has two settings.  Place a small section of hair in each barrette (put the bottom end of the section in it, not up

A played-with Twirly Curls Barbie (left) usually has loose sections of hair.
A doll fresh out of the box has some twisted and secured strands already.

by her head), then put the curler on setting one.  As you press the lever, each strand curls tightly and individually.  Move the curler to setting two, and the two strands will wind around each other.
Since the hair is a little sticky, the strands will stay in place.
A doll fresh out of the box will have some hair already curled and tied with ribbons, as you can see with my Hispanic Barbie.
Henceforth I am calling early 80s hair "Twirly Curls hair."  Contrast it to Barbie's 1990s hair, which is a very dry frizzy platinum that tangles easily.  The curler does not work very well on these tresses--I tried!