sintra how-to guide says to float MEK on it and rub with a rag - supposed to create a finish as smooth as the face...never tried it...
Heres the excerpt from the guide:
VI. Edge Treatment
When Sintra is cut to size during fabrication, edge cells are exposed. Although these cells do
not allow paint or water to be absorbed any further than the first layer, the filling or chemical
collapsing of these cells before painting can offer close to the same texture or appearance as
the surface of the sheet after painting.
A. Filling exposed cells (10-19 mm)
Spot putty or glazing compound used in the auto body industry works very well.
1. Fill edge cells with spot putty using a stiff, flat blade. Fill the cells, do not build up the edge.
2. When dry, usually 3-4 minutes, sand lightly to remove blade marks and any build up of
putty.
B. Collapsing exposed cells (1-6 mm)
Use a PVC solvent such as, Methyl Ethyl Ketone (MEK) or Tetrahydrofuran (THF).
1. Sand edge of Sintra to remove all saw or router marks.
2. Apply PVC solvent to sanded edge with acrylic glue applicator bottle. With protected
finger, rub solvent onto edge of Sintra. The more you apply and rub, the more cells you
collapse.
C. Edge Banding
For thicker Sintra Material panels, 1 mm or 2 mm Sintra Material can be adhered to the
edge using a PVC solvent.
D. Aluminum or plastic edge extrusions ("U" Channels, T-Moldings)
E. Heat Form
1. V-Rout near edge of panel, approx. 90% penetration
2. Heat Bend
3. Solvent Bond