Differences in PLA

[CrazyIvan]

As a relative newcomer to FDM, I've run into trouble with a reel of PLA I bought.

As you can read in another thread, I bought a Tina2 and it came with a small amount of white PLA. I immediately bought 250g black PLA for initial trials and a first project, which went OK.

I then moved onto another project, this time requiring white. That went well also (even better than the black), until the original sample PLA ran out and I needed some more. After a week (which is several days longer than it should have been), the "white" PLA turned out to be pearlescent rather than flat white.

Is that because the listing said "silk"?

I have M5 internal threads in the current project, which (with the original filament) have been very easy to clean up using an M5 tap. This new filament is a pig to clean up, in fact I have ruined several in the process. Again, is that an expected difference with this "silk" filament?

What should I look for to avoid this problem in the future? Comments welcome.