Bird's nest printing - the dark side of the Force

Hi

After successful first steps with a homebrew LinearItemProfilePrinter
the beast seems to have gone to the dark side of the force...



The good ol' PLA Ingeo 4043D in pure white does produce nice
nopHead Heart shaped boxes (thingiverse thing:61),
as 'shiny' as the one on the right side of my pic.
My new (bad and) black PLA does produce bird's nests only.

The dark side of the (printing) Force:
On the left you see the black frame ... porous ('pitted me')
Center left is the caps inner part... massive, fibrous above layer no. four
Center right is the caps bottom... three "nice" layers (given Temp is right)

- Prints were all done on the same printer with identical mechanical settings...
- The extruder is a DirectDrive Homebrew, a J-Head (0,5mm/3mm) fitted
- Bed was Borosilicate covered with painters tape (Scotch 3434) at room temperature

Using 4043D the temperature setting is non critical...'good' at around 205° (non calibrated)
With the black PLA I did vary the temperature in a wide range
...all result in trouble...
<195° (no calibration) extrusion is difficult (not enough flow)
... 205° give nice first layers (1-3) as in center-right ... from layer 4 cobwebbing starts
>235° and it's all a fibrous birds nest

Calling all experienced Padawans here...
...you got experience with the dark (PLA) side ? - YES Please!
Please explain to me whats happening with black (PLA)
(several good reviews on amazon)
and what I can do to make it work

...and may the (dark) Force be with us