Bronze is standard for many outdoor monuments. Think of the bronze doors of Ghiberti (although a little gold leaf for topping) or the bronze horses at San Marco.
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Thanks…yes, I love bronze, too. This is a tough decision for me. I want to make it myself…not farm the plaque out to someone or to some other device.
This is the type of thing I’d like to use for the marker stone…on which I would put a plaque. Natural bronze basalt bowls.
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Here are my 2 cents based on some experience with outdoor sculpture and a lot of time working with metals.
If you can get a dark enough mark on Titanium for your purpose it will essentially last forever. You are making a very permanent oxide layer on the metal, and it is impervious to almost all environmental factors. Ti oxide it the majority of the pigment in white paint, and it never changes. Thin sheet can be attached to a more substantial backing for a more durable plaque. It is expensive, but not ridiculous. I have made lots of Ti jewelry with metal bought from this company (https://www.reactivemetals.com/titanium).
Anodized Aluminum will last for a long time, but the quality of the dye is very important. The UV component of sunlight will definitely bleach the color and some colors more than others. Make sure to ask your supplier about it being suitable for outdoor use. The other problem with aluminum is that any scratch through the anodized coating will start an irreversible corrosion process. Think about older Aluminum exterior windows. That white dusty stuff is oxidation, and it looks ugly, and when you clean it off you just make it worse. A ground level plaque is going to get scratched, think lawn mowers and string trimmers and even accidental abuse by passers by.
Bronze will oxidize and then last for a VERY long time, but you need to either engrave it very deeply or have a plaque cast. There are also many different kinds of Bronze (and Brass) and they react very differently. For exterior usage “marine” bronze is the most common. Making it yourself on a glowforge with a marking media is only going to last as long as the marking media itself. Again, the scratching issue comes up and any scratches through the media will decrease its adhesion to the metal. If you go this route clean the crap out of the metal surface before you apply the marking media!
Oh, and howdy! I am happy to be able to contribute something since I haven’t used my Glowforge in a while (my wife does though). 
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Nice to hear from you - it has been awhile.
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Thank you so much for all your good info…I really appreciate it and I’m also happy to ‘see’ you again! This entire process is actually quite involved…deciding what material to use and finding the best quality, figuring out what process to use to mark/engrave the plaque…not entirely simple.
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Hey, Josh…again! I looked at the website you linked to and since this plaque I’ll be making doesn’t need to be very large, I feel that a small piece of Ti would be quite affordable. Since their product, “Multi-Etch” seems to only come in a 1 gal. container, I definitely would not be using that, so would have to content myself to whatever engraving I can achieve without it.
My questions, though…
- What would you consider a ‘more substantial backing’…? I’m going to want to adhere it to a smooth section of basalt rock.
- Should I mask it? I have paper masking available.
Any other tips, tricks, wisdom for me, please? Titanium isn’t something that I could afford to do a lot of testing on.
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Oh I was suggesting you mark directly on the Titanium sheet.
Here is an old post (I knew I remembered someone doing this) Gradient testing on titanium and aluminum
As for what to mount t on, how were you planning to attach the metal to the basalt?
If the rock is fairly smooth you might be best off just epoxying the Titanium directly to it (even in thin sheets it is quite stiff).
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One possibility is you could do the BRASS engraving.
then embed or at least coat this sign with stuff from STONECOATCOUNTERTOPS.com
I have several of their products that so far I have not gotten to use. 
However, I have spoken with them on the phone and at least one of their products is UV stable so you could use it to coat the plaque. conceivably you could do a multilayered plaque with brass as the top layer, then coat it.
Good Luck!!!
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Yes…we were considering just epoxying it to the rock. OK…thanks…no masking, then. And, thanks for that link. I don’t even remember that one, but that’s probably because I had no interest at the time in working with Ti. I’ll read it all.
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Thank you for the idea and suggestion. I would however have to ‘mark’ the brass rather than engrave it and from what I’ve been reading, the marking may not last as long as just doing it on Titanium.
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I would do something a bit different than a standard plaque on one of those.
After marking the titanium (I’m a big fan of titanium 
), I’d use a light hammer (like a nylon jeweler’s hammer) and by tapping the titanium into the depression form it to the shape of the basalt bowl. A lot of tapping - you don’t want to go howling-monkey with the hammer. With a thin sheet, you should get near perfect contouring and fitting of the metal to the bowl. Then I’d epoxy it to the stone. Water collection in the bowl shouldn’t bother the titanium one bit and it would be a neat look to see the plate underwater and when it was dry it would still look very special and bespoke.
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Wow…what a cool idea! See?..I would have been afraid to try something like that unless I’d heard that it could be done. I’m daring…(sometimes), but not that daring. Thanks for telling me how to do that…I like that idea a lot!
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OK…now…answers to all these questions has begotten even more questions. I read in their entirety all the threads I could find about this material and still need to know some more stuff.
• How/what do I use to clean Ti before engraving?
• How thin of a sheet would I need to be able to form it to the stone bowl shape, a la @jamesdhatch?
( I read that it is a hard metal, so need a thickness that is maleable)
• And…(can’t believe I’m asking this)…can someone give me a starting point for settings to test engrave, please? I read a post with all sorts of tests and numbers and was completely confused by the time I finished.
I’m feeling like a beginner. No…wait…of course, I am one.
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It’s a common technique used in custom car fabrication. I would expect anything 22 or 24 gauge or thinner will work. That’s about 0.023"
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Thank you, Jim. That helps me a lot.
Do you have any answers for my other two questions…how do I clean the Ti before engraving…and can you give me some idea of where to begin with settings?
Dish soap (Dawn) and warm water. Or Windex. Or acetone or alcohol. They’ll all work.
Don’t use bleaches or you may discolor the surface.
No idea what to use for settings though. @jkopel might.
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Pretty simple and straightforward. Thank you. I’ll send a message to Josh…hopefully he’ll see it since he’s seldom on here anymore.
@Dan also has experience - Sorry no settings in this link
Trotech laser setting much less powerful than ours.
Hope this helps 
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Thanks for the links. I had already read most of those. That last link that you gave me…the one about ‘marking on uncoated Titanium’ was the same post where I had asked this very same question and for the very same project, four years ago! One member had done many tests on Ti and had listed his settings…however, he was using a 30 W. laser and even though I read his post twice, I couldn’t figure what the heck he was talking about, so I was back at square one.
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