Corel Draw setting for glass?

[Keith Upton]

Several days ago I thought I read something about either a contour or inverting the image before laser engraving it on glass. But now I can't remember where I saw it or what it actually said. Am I way out in left field with this, or is there some trick evolving that stuff?

[Mark Sipes]

I don't recall the posting you are referring to Not sure why anyone would invert ( make a negative) of an image to print on glass. As for contouring.. that is shaping tool that may be used for just about any graphic but regarding glass specifically.. ????.

[David Somers]

Any possibility they were referring to etching on the back side of a piece of glass rather than the front side?

[Dan Hintz]

Ah, so reversing the image, not inverting it... that would make more sense.

[Dee Gallo]

Why wouldn't you invert the image? It seems to me anything black will engrave, giving you a frosted line or area. So you want to invert the image (make it negative) to get your white areas to look frosted and your black area to be clear (and appear darker). You would ALSO want to flip it if you are engraving the back of the glass.

So unless you WANT the black parts of the engraving to appear frosted, you would invert it.

That's my 2¢ FWIW

[Vic Velcro]

... unless you WANT the black parts of the engraving to appear frosted, you would invert it.

On occassion, I have rastered on glass opting for the blacks to be 'frosted'. I have done this when I used ink to fill the frosted areas with black or with color. When I did not intend to fill those areas with ink, I did invert the image before running the job. As Dee indicates, the effect has a better appearance (if not using ink to fill).

[Dan Hintz]

Part of the confusion is the OP has not mentioned (as far as I can tell) whatis being engraved. If it's text, then typically you do not invert B/W... if its an image, then inversion may be necessary to get a proper looking result. When I think of glass, my mind wanders to awards or simple text of one form or another.

[Keith Upton]

You are quite right Dan, I should have said for images or artwork. The actual artwork I had in mind were these:







If I want the black areas to appear darker, I should invert the images correct? If I do that, everything white here (these files have no actual background colors (they are transparent)) will be lasered and appear as frosted on the glass (front engraving in my case) correct?

Also, when I invert one of the images above in Corel, the black ares turn a light gray and nothing happens to the white areas... is that correct?

Thanks again for all the help.

[Mark Sipes]

Inverted like this?

[Mark Sipes]

The dog fight does not appear to be fair since the Brits are flying a jet...

[Keith Upton]

Inverted like this?

That's not how mine looks in Corel when I use the Invert effect. The white areas stay white and the black areas are turn a light grey.

The dog fight does not appear to be fair since the Brits are flying a jet...

Yeah, lol. That was actually a shot of the artwork with out the prop visible to show the details behind it a little better. The final version does have the prop

[Dan Hintz]

That's not how mine looks in Corel when I use the Invert effect. The white areas stay white and the black areas are turn a light grey.

Change to a 1-bit colorspace before or/after you invert... if black is turning to gray, sounds like you didn't have black to begin with. Also, make sure you're running RGB, not CMYK.

[Keith Upton]

Thanks Dan, I'm new to CD... I'm an AI guy

[Keith Upton]

You were correct Dan, even those that artwork was drawn in black in AI, Corel did not show it as true black. I corrected that and now when I invert it, the black artwork turns white and you can no longer see it on the screen. The clear areas did not change, which I expected since there is nothing there to invert. But that leads me to think that if I send this inverted image to the laser, nothing is going to "print".

So does this inverting trick only work on gray scale images like photographs and such?

[Dan Hintz]

You were correct Dan, even those that artwork was drawn in black in AI, Corel did not show it as true black. I corrected that and now when I invert it, the black artwork turns white and you can no longer see it on the screen. The clear areas did not change, which I expected since there is nothing there to invert. But that leads me to think that if I send this inverted image to the laser, nothing is going to "print".

So does this inverting trick only work on gray scale images like photographs and such?

It's a function of the substrate your engraving on, as well as the look you're after. For example, when engraving an award on glass, I want the text to be engraved... so it needs to be black in the image I send to the enngraver. Same with black marble. But we're used to seeing black text on a white background when it's viewed on the screen, so it can be passed directly to the engraver.

An image, however, is usually viewed with light areas viewed as light, dark viewed as dark, etc. If we sent that over to the engraver as is, the dark portions in the image would engrave as a light color (and vice versa). So for photos, it's typical to invert the colors. But what if we're engraving a light substrate, like a piece of white tile? In that case you would likely send the image over "as is" and color fill with black ink... black on the screen appears black on the engraving.