No more exacto knife!
Cutting a mask is about to get simple.
Nice fix for a universal problem. I notice “clean” just after I dump a handful of dinner’s silverware into the basket of clean… wow, those glasses look shiny.
Oh well, can’t be too clean - run it again.
wow, that is expensive tape! My transfer tape is nearly half that price (transferRite from signwarehouse)
Somewhere I thought there was a comment in a topic about using the masking to cover a clear material so that the camera could register its height properly. Can’t find it anywhere. So @jdodds, I understand your question as it relates to the Glowforge. I’ll keep looking.
Unless the tape has a pattern printed on it, I would think it would be difficult to use it as a focus target.
I believe TransferRite is laser-safe, at least the 582U and the 592U (medium- and high- tac)
It is made by American Biltrite Inc., who call it a “protective paper laser masking” and are one of the only tape manufacturers that I have seen who have an MSDS available.
American Biltrite_6000_series _ULTRA[2015-11-01].pdf (154.4 KB)
Fantastic!! Thank you! You just saved me some $$!
I can’t find it either. I doubt they used a pre-mask to etch the back of the ipad, but that surface probably has a lot of the same characteristics as pre-mask tape from an optical sensing perspective. The camera on the Glowforge would have to be dynamically sense for the surface height for correct distance over the entirety of the curved edge surface. Wood on the other hand probably doesn’t have the same light reflective characteristics as pre-mask tape and forbon, definitely not.
USCutter has paper transfer tape in rolls of various sizes too… also much cheaper than Laserbits.
I don’t know for sure if any of the sign industry tapes are laser safe, but I suspect that any paper-based tape is probably OK.
If you look in the specifications tab at US Cutter you can see the adhesive type, at least on some products. For example, this one specifies latex adhesive. Paper plus latex seems like it ought to be laser-safe.
http://www.uscutter.com/Main-Tape-GXP750-PerfecTear-Plus-Medium-Tack-Transfer-Tape
Ahhhhh. . . . . Run, there’s been a hijacking! ! ! 
One of the hijackers here… sorry for the delay… we will try and get you to your original intended destination.
Aside from the glowforge official materials (which of course have the material id codes on the masking) I would imagine that anything opaque and matte would read similar to masked material. Translucent and or reflective materials could potentially cause more of an issue for the optics.
I would hope that between the two cameras, the ramp-able interior lighting, and some trick computer-vision, that focus-precision will not be affected one way or the other by masking.
Maybe someone at the GF office can give a simple answer:
@aeva or @madebynick, can the glowforge “see” a piece of clear acrylic with no masking on it?
Maybe I shouldn’t assume but I thought blue painters tape or regular masking tape would work fine
It probably will, but it is probably going to be more expensive than large rolls of material made for this purpose.
Let’s take it a step further: can the cameras judge distance on masking with no features, i.e., solid color?
I just hope that manual focus will be an option. (I searched the forum a little, but I didn’t come across a definitive answer.)
I’m assuming most of the material I cut will be flat, so I hope I can just set up the machine to make the cut at a static focal distance so it doesn’t automatically “fix” the focal distance “for” me.
Defocusing has been spoken of quite a bit, by Dan as well, so I’d imagine one would have the ability to focus as desired, if desired. Either way, focus should be close to a non-issue in most cases.
Digital cameras are performing autofocus based on either a contrast detection algorithm or phase detection. Given the fact GF is largely using smartphone technology, I’d imagine it’s contrast based autofocus, which is a bit slower but more accurate, and quite a bit cheaper to implement technology wise.
So, solid color I would say absolutely no problem. It’s going to detect a contrast difference between either the grate or bottom of the case - edge detection per se. A straight translucent material may pose a problem due to lack of contrast unless perhaps the lights in the housing provide an apparent difference in contrast.
I’d say general rule of thumb is if you could get your smartphone to focus, the GF will focus.
I’d imagine what you’re seeing through the preview screen before printing is provided by the cameras, so you should know pretty quickly whether the material image looks in-focus or out of focus and whether you need to manual focus. That’s assuming flat material.
I asked a question in another thread about laser focus. In the camera world we call it depth of field - which is basically the z-depth of what’s sharp enough to be considered in focus. I don’t know what it’s called in the laser world. Is the laser depth of field, so to speak, deep enough it could run over the slight curve of a MacBook without needing to change focus? I don’t know. Beta test me and I’ll throw my MacBook in 
I agree, contrast detection will work fine if the item is flat and small enough for the camera to see its edges. But what about a large sheet filling the workspace, or a non-flat smaller piece? How would the camera sense the distance to a curved surface if it has no visual features? Do you suppose it uses an auxiliary focusing beam that the camera can lock on to?
it would be pretty easy and cheap to implement an AF assist beam.
Probably not. We recommend using acrylic with masking paper. You would be able to enter the thickness manually, though.
Thanks, Dan for answering this on the live broadcast. Long story short, yes there is a focus assist beam!