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Post by stephan on Oct 20, 2021 15:16:41 GMT -5
jasoninsd hummingbirdstones you both got me curious, so I read up on the chemistry of cyanoacrylate curing (yes, I'm a nerd), and I found something interesting. The reaction requires a little bit of water. And here I am, making sure the stones are absolutely dry, when the air here has been bone dry, lately. So what the accelerator does (at least, in part), is to increase the local relative humidity by dropping the temperature (which is how dry ice makes fog, so Jason's dry ice comment was right on point). Some accelerators also contain acetone . to speed the solvent evaporation, which is weird, because more acetone will soften the glue. But... before we go absolving thinner superglues of their responsibility, they are mostly "ECA" which is a monomer precursor to the final product. Gel versions are up to about 10% polymethacrylate (so, already partially polymerized to make it more viscous, and to give the curing reaction multiple nucleation sites). So, we'll blame cheap glue and dry weather. That "I'm intrigued" meme is so bloody familiar, but my brain won't give up the info. Remind me....
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Post by stephan on Oct 20, 2021 18:05:32 GMT -5
Thank you sir, welcome back! |
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Post by holajonathan on Oct 20, 2021 19:07:30 GMT -5
Nice work. Two major take aways from having looking at lots and lots of your cabs: 1. It is often worth cabbing soft / fractured / problematic parts of a slab, because those are often the most interesting parts. I would have avoided the hematite band because it usually undercuts. You took the risk and it worked well to add contrast. 2. Color / pattern / composition matter more than the shape of the cab. Your approach is to find your favorite area of rock and to frame it in a way that does not distract from what makes the rock interesting. The Botswana agate cab you posted is an example of that. I can't say I'll be making a template of that shape, but it does not distract from the rock itself, rendering it a success in my book. You use a lot of straight edges in your free-forms, which adds visual "order" to unsymmetrical shapes. |
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Post by holajonathan on Oct 20, 2021 19:27:27 GMT -5
stephenAs you know, camera autofocus, even on DSLRs, struggles with polished cabs. There is no easy solution "in the field," where manual focusing is difficult. Although your photos are generally good, you fall victim on occasion to the camera focusing on your hand and not the cab. Have you tried a really high aperture number? (f16 or even f22) I know most lenses are sharpest around f9-ish, but whatever you lose in optical sharpness would probably be more than compensated for my the deeper focal plane. The focus plane should be deep enough at f16 or f22 that the cab will be well focused even if autofocus is latching onto your hand, and not the cab. This is more me thinking out loud than offering advice specifically to you. Perhaps something for me to experiment with and report back.
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Post by jasoninsd on Oct 20, 2021 20:12:06 GMT -5
stephan - I have no clue where the "I'm intrigued" meme originated. That character looks familiar to me as well...but I can't place it either.
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Post by hummingbirdstones on Oct 20, 2021 21:58:50 GMT -5
I know one or both of you have isopropyl alcohol at home. Try it and report back, please!  |
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Post by jasoninsd on Oct 20, 2021 22:11:34 GMT -5
I know one or both of you have isopropyl alcohol at home. Try it and report back, please! Thanks for posting this! Will do!!!   |
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Post by stephan on Oct 20, 2021 22:13:42 GMT -5
It was hard to get back when people were hoarding, well, everything, but back in stock now. 😁
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Post by stephan on Oct 20, 2021 22:40:49 GMT -5
holajonathan I’ve experimented some with aperture priority photography, but haven’t really gotten good at doing it one-handed, holding the cab with the other. Still experimenting, but so far, I’ve gotten the best results with auto-focus, even with last-second focus shifts and wonky white balance. You’re right, I’ve done mostly F9, because that’s what I’ve had the best luck with on my primary subjects — bees and dragonflies. I’ll have to try f22 for cabs (and maybe build a light box). As for the cab design — I’m totally willing to take a chance on breakage or undercutting to chase a good design. Often, with patience and care, it works out. It tends to be the fractures I didn’t see that cause problems.
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Post by holajonathan on Oct 20, 2021 23:15:45 GMT -5
holajonathan I’ve experimented some with aperture priority photography, but haven’t really gotten good at doing it one-handed, holding the cab with the other. Still experimenting, but so far, I’ve gotten the best results with auto-focus, even with last-second focus shifts and wonky white balance. You’re right, I’ve done mostly F9, because that’s what I’ve had the best luck with on my primary subjects — bees and dragonflies. I’ll have to try f22 for cabs (and maybe build a light box). As for the cab design — I’m totally willing to take a chance on breakage or undercutting to chase a good design. Often, with patience and care, it works out. It tends to be the fractures I didn’t see that cause problems. Auto focus with a manually selected the focus point on a DSRL helps, but sometimes the camera still wants to focus on something being reflected onto the cab surface. Solid colored, shiny objects are pretty much impossibly for any autofocus system, although autofocus can usually lock on to the very edge of such cabs. I like outdoor cab photos, or better yet, indoor by a bright window. Light boxes work well for capturing the cab in the most neutral way possible, but I like a good reflection on part of the cab to show the shine. I'm just wondering if a tiny aperture (deep focusing plane), and allowing the camera to focus on a hand, might take all the guesswork out of it. I have shot macro with f16 and f22, and even though lab results will show that lens optics are distorted at extreme apertures (large or small), real world results were good. |
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Post by stephan on Nov 7, 2021 19:46:45 GMT -5
I received a generous gift of a SFRB of nice, fat (1cm thick) plasma agate slabs from paulshiroma , and needed to check it out. I free-formed a piece that I was able to snap off one of the slabs.  DSC_0819_Large plasma agate freeform by Stephan T., on Flickr 80mmx38mmx9mm Given its reputation for under-cutting, I went slowly, and experienced very few issues. It behaved mainly like an agate with substantial inclusions would be expected to. Some areas felt softer, but with a light touch, they held up well. The make-up of plasma agate reads like the ingredients list on a bag of potato chips... "May contain one or more of the following...." In this case those possible "ingredients" include chalcedony, quartz, jade, serpentine, cinnabar, chromite, hematite and others. It is only found in the Clear Creek Recreation Area in San Benito County, CA. Shinier in-person than in the pic -- I actually deliberately oriented it to minimize glare, as first attempts at pictures were completely washed out. I definitely want to do something more with this. It's probably a bit heavy for the glue tabs I usually use, though they are available in larger sizes. I think it would look good drilled with only a thong looped through the hole, but I'm a bit hesitant to do that with a finished piece. If I had a Gryphette, I'd consider a groove wrap, since the slabs are thick enough for a nice dome as well as a good, thick girdle. ETA: working this cab was a wonderful way to decompress from a brutal week. |
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Post by jasoninsd on Nov 7, 2021 21:41:37 GMT -5
Stephan - you did a fantastic job working this material! That cab looks amazing. Did you do anything else besides using a "light touch"?
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Post by stephan on Nov 7, 2021 21:58:44 GMT -5
jasoninsd old wheels with a spray bottle instead of geysers (yup, I still haven’t gotten around to getting the aquarium pump). It got warm on on the Nova wheels. Not as hot as I’d let jade get, but a similar principle. Took it up to 14000, which is now broken in, thanks to Prairie and Crazy Lace agates.
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Post by jasoninsd on Nov 7, 2021 22:12:29 GMT -5
jasoninsd old wheels with a spray bottle instead of geysers (yup, I still haven’t gotten around to getting the aquarium pump). It got warm on on the Nova wheels. Not as hot as I’d let jade get, but a similar principle. Took it up to 14000, which is now broken in, thanks to Prairie and Crazy Lace agates. Interesting. I was thinking that maybe I was getting the undercutting due to the temps it was reaching on the buffing pad... Well. Back to the drawing board. LOL |
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Post by stephan on Nov 7, 2021 23:01:01 GMT -5
It’s weird… the bald wheels seem to have more “stickiness,” so they really pluck out moss, but work well on other material. I also cut a cab of some of the Graveyard Point you sent — no undercutting there, and such a shine that I haven’t managed a picture that wasn’t my reflection… stay tuned.
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Post by paulshiroma on Nov 8, 2021 12:16:52 GMT -5
Great cabs, Stephan!
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Post by stephan on Nov 9, 2021 23:54:16 GMT -5
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Post by jasoninsd on Nov 10, 2021 2:12:34 GMT -5
Another group of great looking cabs Stephan! I just freaking love the looks of polished Prairie Agate! However, that Root Beer is WAY more than some UBR! |
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Post by stephan on Nov 12, 2021 20:51:21 GMT -5
Lost this one for a while:  DSC_0843_Humboldt Coast jade by Stephan T., on Flickr I collected and cut this years ago (there should be another 1-cab slablet or two somewhere, but it was a small cobble) on Agate Beach, at the recently renamed Sue-meg State Park. While it doesn't look like typical California Coast jade (nephrite), it does seem to be a rare piece of jadeite. It polishes like it, makes slightly "foamy" swarf like jade, and has a specific gravity of 3.32 -- right smack-dab in the middle of the jadeite range. It is primarily white jade, with some dark green. The yellow in the healed fractures may or may not be jade |
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Post by rockjunquie on Nov 12, 2021 21:19:28 GMT -5
Nice! I really like that.
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