Question about acrylic

If you do a deep etch on translucent/frosted or opaque acrylic, is the etched part more translucent than the full thickness part? Or does the etching darken the material, even though those spots are thinner? Does that make any sense at all?

I’m terrible at explaining myself. Like, you know how when you carve a pumpkin, the deeper you carve without cutting through, the more glowy that part is when it’s backlit. I was wondering if the same thing is true of not-transparent acrylic. I tried googling, but that’s a beast to try and Google. For my sleep-addled brain, at least.

So any lasery-experienced people know?

5 Likes

I don’t have a laser yet so this is strictly based on my casual observation; take it for what it’s worth. :slight_smile: In all the examples I’ve seen, the etched part of the acrylic becomes white and opaque.
They etched areas reflect the light differently and that’s what you see on the LED acrylic signs.


8 Likes

Right. On clear/transparent acrylic, the etched part is more opaque than the nonetched part (though not totally opaque, I think?). But I was wondering if the reduced thickness on opaque or translucent acrylic might let light through compared to the surrounding material, or if the texture of the etch blocks light (in which case, I guess on translucent acrylic you could still get the same effect, just oppositely…).

Like if you took opaque white acrylic, and did a deep etch, a medium etch, and a shallow etch, and then held it up to the light, would you have different “shades” from the various depths?

3 Likes

Aww, I see what you mean now… Hmm, good question. It would make sense that the thinner areas would let more light shine through, I just wonder if you can etch without causing the white/opaque effect. I know you can cut clearly, just not sure about etching. It’ll be interesting to see what some of the experts have to say.

1 Like

With a low lpi, I’d guess the etching effect would be to scatter more light, therefore make it ‘whiter’.
On a higher lpi, the melting effect of the beam might overlap and produce a smoother surface, therefore less whitening.
Then when you hold it up to the light, the first case might actually look darker, but the second, lighter.
Doing the same thing with a translucent material might produce the same result, but the numbers would need to be different.

Or possibly totally wrong. Guessing is a poor substitute for knowledge.
:upside_down:

4 Likes

I don’t have a laser, so I can’t test this yet, but here is my understanding.

Cast acrylic will turn white when etched. You should be able to flame polish it back to it’s original color/clarity.

As for the the light transmission, it really depends on the colorant they used. If visible light can penetrate the colorant somewhat, then your technique should work; thinner sections would be brighter than thicker sections. I’d imagine you wouldn’t have much success with a black acrylic, but should for white, maybe.

6 Likes

One thing I want to try is defocusing the beam to see if that would act as a flame polish on an engraved section.

4 Likes

paging @smcgathyfay, she is our resident expert in these sorts of materials

6 Likes

It does to a large extent but there appears to be a Glowforge specific problem that causes ripples. See this thread: More trial, errors, and fun

5 Likes

The deeper the etch the better the refraction you get from edge lighting. It’s actually a technique to be used in complex designs to etch different parts of the design with different power levels to get more or less definition to the design when the light hits it.

It’s one reason why 1/4" or 1/2" acrylic makes “better” LED lit signs/plaques/whatever than 1/8". I’m looking forward to the GF’s flip feature so I can do some interesting stuff with proper alignment of front and back engravings (front face engravings don’t do much in the light diffusion realm which is why you usually engrave those edge lit signs from the back - but I can see the potential for some mixed effect designs using well aligned front & back engravings).

3 Likes

Havent made it into the office yet today but I will certainly do some testing…
I would think that your theory is correct…the thinner the material, the possibility of more light coming through on translucent acrylic…not sure about the opaque. However, on cast, the etching does turn it whitish…I do have some color extruded I could test on…
Report back later today…

7 Likes

Really hard to get a photo of this, but this is with red extruded 1/8" Acrtlite.

The depths are .013", .023" and .038"


15 Likes

I think its preference…I prefer to barely etch the surface as it gets really white. And lights up best imo.

4 Likes

Ah! Thank you. You’re amazing!

2 Likes

If the depth map printing ends up working well (and on acrylic), maybe we can do something like these:

I’ve 3D printed several and they’re a big hit - they look great hanging in windows.

10 Likes

This was brought up before, but haven’t seen it mentioned since.

1 Like

I’ve got some white Corian that is waiting for this application.

1 Like

I sort of figured thats where @erin was going with this idea…not sure the depth difference will be enough to do that…
On the ones you’ve done, how thick do you need to do for the black areas? And what about the thinnest part…whats the depth difference between the two??

@smcgathyfay Thank you so much for this visual. Wonderful example. I just received my GF about a week ago and have a strong interest in working with acrylics and creating stained glass effects with cutting and painting. I’ve only had the chance to test one simple etching onto a small section of leather. Today, I’ll be exploring on my 2 acrylic sheets. I’m an design artist and will be using it to etch and cut my detailed designs to create the illusion of stained glass and etched glass. I’m planning to currently place designs in a shadow box with LED light strips to light it. I’d love any advice or ideas regarding ways to LED blacklight light acrylic and mounting ideas. I’m also interested in making fountains and lamps with my designs. For now, I’m starting simple. I’ll share my results when I’m satisfied with them to the forum. :slight_smile:My IG account with some GF etched Designs of mine

1 Like