Glass Etching / Round Seal

[Dan Park]

Hello Everyone:

I have a quick question for you. I'm etching a round shape on a pint glass and when I etch it at either a fast speed or slow I get an oval shape result. But when I etch the same design on a flat piece of glass, it comes out perfect.

Can someone tell me why I get an oval verse a circle on the glass? Thank you

Dan

[Albert Nix]

Are you using a rotor attachment? If not and you are tring to engrave to close to the edges of the diameter of the glass it is simply trying to drop off and it will elongate.

[David Fairfield]

As long as the resulting oval is consistent, you can scale the image to compensate for the distortion, so that it will engrave as a circle.

Dave

[Martin Boekers]

I've had that issue too I used to believe to be an optical illusion as if you look straight on to the round glass it condenses the angle of view thereby it gives the illusion of pushing the sides a bit together.

You can check this by engraving circle on something flexible and wrapping it around the glass and see if it looks different than laying flat.

Sometimes though it is more pronounced than that explanation will cover.

So I tend to blame it on "slipage" when that happens.


Marty

[Kim Vellore]

I have a theory that the X dpi resolution is better than Y dpi this difference shows up as a oval, one way to find out is to raster a circle and vector around the circle, since the vector is not DPI dependent you can see if there is a difference. When you are at it do the same changing the DPI, to see if one DPI works better than the other.
Kim

[Tom Delaney]

several months back someone posted a very thorough explanation of engraving that is not perfectly round or straight in the horizontal plane. They even went so far as to provide a formula to calculate the ratio that you would need to adjust your work so that it winds up circular. Most people simply figured they would keep adjusting the width of the engraving until it looked right.