I am currently preparing to encapsulate a 19th century painted silk labor banner.  The silk crepeline I was preparing to dye creates a moiré effect when positioned on top of the banner.  The only time the moiré does not occur is when the crepeline is laid on the banner off grain/bias.  Unfortunately, the textile is too large to use this technique without creating a diagonal seam across the surface.  Does anyone have any insight on eliminating the moiré effect?