Grocery store PLA is weird

[Refrigerator]

Just a few days ago i finished my third 3D printer and wanted to test it out yet had no filament, until i remembered that i had some PLA from the grocery store.
I don't know what flavor of PLA it is but it's meant for 3D pens and was located in the toy section and comes in a pack of 3 different colours in 3m lenghts each, 9m in total.
3m of filament is enough for a small test so i decided to print a test cube to see if my settings are correct.
The print came in undersize, turns out i forgot that i have 16T pulleys, not 20T.
But the plastic was super weird. I decided to give it a squeeze with some pliers to see how tough it is and it immediately cracked apart.
AFAIK normally prints separate at the layers but in this case the cracks went every way and layer lines couldn't even be distinguished.
The surface at the crack looked like glass - completely smooth. I thought that maybe the plastic is just brittle but with a knife it cuts like butter.
Printed another test cube with some pink coloured filament and when pulling it off my glass bed it fractured the bottom of the print (and also pulled some glass off dang it).
The fracture caused the bottom to become opalescent, which i thought was really neat.
I'm very new to 3D printing still but i thought this was cool enough to share.

Ps: last 4 pics are the opalescent print from different angles.

[vintagepc]

Are you sure it's actually PLA (or pure)?

Some manufacturers will put in additives so that it is more suited to 3D pens than printers to lower the temperature at which it prints and so that it flows better (more on this in a bit)

Many pen filaments are also actually PCL which has a much lower melting point so it is considered "safer" for a pen where kids may be handling it; while you can still burn yourself at 60C it's obviously going to be a lot less severe than if with a pen tip at 180 or 200C.

As for the cracking... PLA is brittle and will fracture like that. If it's breaking in this way instead of along the layer lines it means you have good layer adhesion and might even be printing on the "too hot" side for the material - essentially cooking it and making it more brittle. I'd suggest running off a temperature tower if you want to continue using it.

The fact it took a chunk of glass with it makes me suspect you may have a blend containing PETG as this material is particularly notorious for bonding VERY well to glass. (and it's also sometimes used to give those "silk" filaments their particular flow characteristics and opalescence.)

[Refrigerator]

Are you sure it's actually PLA (or pure)?

Some manufacturers will put in additives so that it is more suited to 3D pens than printers to lower the temperature at which it prints and so that it flows better (more on this in a bit)

Many pen filaments are also actually PCL which has a much lower melting point so it is considered "safer" for a pen where kids may be handling it; while you can still burn yourself at 60C it's obviously going to be a lot less severe than if with a pen tip at 180 or 200C.

As for the cracking... PLA is brittle and will fracture like that. If it's breaking in this way instead of along the layer lines it means you have good layer adhesion and might even be printing on the "too hot" side for the material - essentially cooking it and making it more brittle. I'd suggest running off a temperature tower if you want to continue using it.

The fact it took a chunk of glass with it makes me suspect you may have a blend containing PETG as this material is particularly notorious for bonding VERY well to glass. (and it's also sometimes used to give those "silk" filaments their particular flow characteristics and opalescence.)

Says PLA on the packet but i don't know what other spices they might be mixing in.
Regardless, i won't be using it anymore because i received the 10kg spool of PLA i had ordered.