<p>Are there any techniques for getting a smooth finish for parts printed with co-polyester (PET) filaments? More specifically, I am looking for an alternative that does not roughen the look of the part - such as using sandpaper - but rather works like acetone baths for ABS.</p>

<p>In particular, I want to treat ColorFabb's XT filament made from the <a href="http://www.eastman.com/Markets/3D_Printing/Pages/Products.aspx" rel="nofollow">Eastman Amphora™ 3D polymer</a> (<a href="http://ws.eastman.com/ProductCatalogApps/PageControllers/ProdDatasheet_PC.aspx?Product=71100831&amp;sCategoryName=Generic" rel="nofollow">datasheet</a>). This is also the polymer is also used in:</p>

<ul>
<li>ColorFabb <a href="http://colorfabb.com/co-polyesters" rel="nofollow">nGen and XT</a></li>
<li>Taulman3D n-vent</li>
<li>TripTech Athiri 1800</li>
<li>3DXTech 3DXNano</li>
</ul>

I've found a
chart
which covers several plastics and solvents and only two of them (
Chloromethane
and
Chloroform
) are rated "D" which includes dissolving the material and both seem to be quite nasty and I doubt you will be able to purchase them without being placed on several lists.
Is it possible that something like
XTC-3D
from Smooth-On would work for you?
Also some more information on dissolving PET
here
, several sources also mention PET is affected by Hydrogen Peroxide but they do not mention to what degree the plastic is affected.