Identifying abs and pla

[sdtag]

how can I tell if something I printed 6 months ago was printed in abs or pla?
I'm thinking it's going to be destructive, like wipe some acetone on a spot and if it dissolves it's abs.
If it doesn't it's pla. (?)
is there a better way?

[jfkansas]

Yep, put a little acetone on the bottom.

[curious aardvark]

even better - if it's dull and lifeless looking and a little rough to the touch: it's abs.

If it's smooth and shiny and hard, it's probably pla.

[Mjolinor]

A scanning electron microscope could do it I think.

[sdtag]

lately I've been getting some pretty smooth and glossy prints using abs. Some pretty wicked curls too on the longer prints too. I think I'm extruding too hot. And my bed won't go over 90c. Some of my abs and pla spools are the same color so I just wanted to know if there was a tried and true method already, other than an electron microscope.
looks like acetone will be my test.
thanks everyone.

[Mjolinor]

lately I've been getting some pretty smooth and glossy prints using abs. Some pretty wicked curls too on the longer prints too. I think I'm extruding too hot. And my bed won't go over 90c. Some of my abs and pla spools are the same color so I just wanted to know if there was a tried and true method already, other than an electron microscope.
looks like acetone will be my test.
thanks everyone.

Damn, I was just hoping you would have one I could use.

[awerby]

You could do a hot needle test. Put a red-hot needle to an inconspicuous part of the print. Smell the smoke. Compare the smell to known samples of both materials; the difference should be pretty obvious.

[curious aardvark]

bear in mind that acetone will - apparently - soften pla.

Your best bet is to get a marker pen and stick an A or a P - on the bottom of your prints when you've done them.

Or do what I did and just not use abs :-)

[sdtag]

I have been using abs mostly and living with the curls. Now I am getting back into PLA again. And yes, it definitely is glossier than ABS.
And I really really like how PLA doesn't curl. But I get strings.
I am at 215C at the nozzle and 60C on the bed.
I am printing at .25 layer height at a speed of 24. I am retracting to 8 mm. It was originally set to 6.
Why am I getting strings? Is the nozzle still too hot? I guess I need to do some testing before I make anything else.
You guys who love PLA, (ca) what are your temperatures, distances, and speeds? I know it's a little different for different machines and filaments, but give me a starting point please.
tia

[Ama-fessional Molder]

A rough finish on ABS is due to excessive moisture content. Properly dried, extruded ABS cools to a nice glossy finish just like PLA should. The different is that PLA isn't nearly as affected by water.