Erase Blend Mode Shows Edges

[jbartley]

Why when I place a vector object over another object with the blending mode is set to erase I can still see the online of the object underneath? The edge of the circle is still visible when the rectangle is being used as a vector mask and set to erase. 

This happens also to the edge of photos as well when I select this type of blending mode. I thought it may be a screen artifact, but it prints as well.

 

[thomaso]

12 hours ago, jbartley said:

the circle is still visible when the rectangle is being used as a vector mask and set to erase. 

It simply depends on the way you position the layers. If you move a layer underneath and inside another then it gets placed INSIDE, so the stroke of the one above remains visible.
If you instead don't place both layers inside one of the other but group them you might get what you want (violet):

 

Whereas for masking a layer you don't need a blend mode "Erase" but simply mask the visible part to hide the other:
Note that a stroke of the masking rectangle (above) remains visible where it is congruent with the masked objects edge:

 

 

[jbartley]

I've marked with arrows to point out the line from the underlying circle that is showing up when erase is applied.

I see from your example how to achieve the mask. Thank you for the explanation.

But why would the underlying edge showing if erase is selected. Seems like a bug to me.

 

 

 

[thomaso]

Yes, I have seen the thin grey line before and therefore I made the stroke in my sample objects wider.

Again, as mentioned: Your visible grey line appears to be the stroke you had assigned to the circle object. Its visibility is related to the position of your erasing layer: because you placed the erasing rectangle INSIDE the circle it erases only INSIDE. The stroke of a shape is not inside.