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Mediospirifer

Just a quick update on the samples I'm trying this with...

 

Both sets of specimens (Ordovician brachs & Devonian corals/bryos) are currently sitting in caustic baths. There was a 1 month hiatus when those of us involved went on vacation, but now we're all back and seeing how things develop.

 

Before the vacations, we had a small amount of debris shed from both sets. The Devonian bryos in particular showed more detail after a turn or two in the bath. This Tuesday, the brachs were showing more detail than before. As of today, I see more sediment in the bottom of both baths, so we're going to continue the soaking. I'll next have a look on Monday.

 

At this point, I'd say the technique works, slowly. It does seem to bleach the Windom fossils, too.

 

I'll see if I can get photos on Monday of the progress so far. Unfortunately, my computer at home has become unresponsive, so my only reliable access to the Forum is at work. Since I don't work on Fridays, I won't be commenting after I leave tonight until Monday.

 

Further updates when I have more progress to report.

 

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Peat Burns
2 minutes ago, Mediospirifer said:

Just a quick update on the samples I'm trying this with...

 

Both sets of specimens (Ordovician brachs & Devonian corals/bryos) are currently sitting in caustic baths. There was a 1 month hiatus when those of us involved went on vacation, but now we're all back and seeing how things develop.

 

Before the vacations, we had a small amount of debris shed from both sets. The Devonian bryos in particular showed more detail after a turn or two in the bath. This Tuesday, the brachs were showing more detail than before. As of today, I see more sediment in the bottom of both baths, so we're going to continue the soaking. I'll next have a look on Monday.

 

At this point, I'd say the technique works, slowly. It does seem to bleach the Windom fossils, too.

 

I'll see if I can get photos on Monday of the progress so far. Unfortunately, my computer at home has become unresponsive, so my only reliable access to the Forum is at work. Since I don't work on Fridays, I won't be commenting after I leave tonight until Monday.

 

Further updates when I have more progress to report.

 

Are you applying the flakes directly to the fossils?  This works much better and faster than a bath.  Also, I soak my fossils in water for several days after KOH treatment.  This draws out the KOH.  The bleaching you're seeing is a precipitate. This will come off with soaking and brushing or air abrasion. 

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Mediospirifer

The KOH we have in the lab is pellets. My colleague prefers to dissolve them rather than crumble them for this experiment.

 

With this latest soak, he did increase the concentration from 10wt% to 15wt%. We'll let them soak over the weekend, and see what they look like on Monday.

 

It's good to know that the bleaching washes off.

 

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Peat Burns
3 minutes ago, Mediospirifer said:

The KOH we have in the lab is pellets. My colleague prefers to dissolve them rather than crumble them for this experiment.

 

With this latest soak, he did increase the concentration from 10wt% to 15wt%. We'll let them soak over the weekend, and see what they look like on Monday.

 

It's good to know that the bleaching washes off.

 

I started with pellets. Had to crush them in a mortar with pestle.  Ended up buying flakes from soap-making suppliers which is much cheaper than lab grade stuff. I tried the bath method with very limited results even at high concentrations. 

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Mediospirifer

Understood. If this does work well, I plan to get some soapmaking flakes for myself. For now, my colleague is doing me a favor, so I'm not going to push for "But I want it done THIS way!". He's the chemist, not me.

 

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Mediospirifer

Well, progress seems to be best measured by how much sediment is in the bottom of the beaker. There's some, but not a lot, and it's hard to tell by looking at most of the fossils whether anything has changed.

 

The Devonian exception is a length of Atactotoechus bryozoan. One side of this specimen has noticeably shed parts of its matrix layer, exposing the detail below. Hopefully, further soakings will remove the rest, in time.

 

The Ordovician brach hash chunks are shedding pieces. Some of the shells are showing nice detail, but I'd have to find my "Before" photos to see how much change there actually is.  At this point, it looks like this is a possibly means to separate hash into decent individual fossils.

 

We're letting the pieces dry overnight; I'll see what they look like tomorrow and give them another bath.

 

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Aurelius
On 17/09/2018 at 10:44 PM, Mediospirifer said:

We're letting the pieces dry overnight; I'll see what they look like tomorrow and give them another bath.

 

Any more updates on this? Did your samples progress any further?  I'm interested in using this KOH on some calcitic ammonites.

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Mediospirifer
2 hours ago, Aurelius said:

Any more updates on this? Did your samples progress any further?  I'm interested in using this KOH on some calcitic ammonites.

 

Yes, we have some good progress. :D I would have posted an update last week (or earlier), but my colleague went on a week-long conference trip to Australia without forewarning me, and left the rock in solution while he was gone. Today is the first I've seen him since my last post.

 

At present, the Ordovician hash pieces have mostly separated into the component shell pieces. I'll have to soak them in water and scrub them to get the residue off before I can really see how the fine details of ornamentation fared, but it looks good to the naked eye.

 

The Devonian pieces have shed a significant amount of residue. There are 3 pieces: a partial horn coral, a knob-shaped smaller coral, and a short piece of Atactotoechus bryozoan. All three have shed matrix. In particular, the knob-shaped coral has lost a lot of the matrix that was clogging its pores, so they are now reasonably defined pits. And the bryozoan has shed enough matrix that I can now see the Aulopora specimen encrusting one side!

 

I'm going to continue soaking them to see how clean I can get them. So far, I'm happy! Even if it does take a long time to get results.

 

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Mediospirifer
3 hours ago, Aurelius said:

Any more updates on this? Did your samples progress any further?  I'm interested in using this KOH on some calcitic ammonites.

 

By the way, I'd advise trying it on one sample that you're willing to see damaged, just to make sure of the effects before treating your more-prized specimens. Just on general principles.

 

Good luck!

 

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Mediospirifer

A little follow-up to yesterday...

 

I looked at the fossils under a loupe today, and noticed several things. The Ordovician specimens still have matrix crusted on them, but where the shell structure is exposed, the fine growth lines are visible. The shells appear to not be damaged by this treatment. My Devonian horn coral has a couple of tiny crinoid holdfasts becoming visible, and an almost botryoidal surface structure in the cup. The club-shaped coral has lost a lot of the matrix clogging its pores. And the bryozoan also has lost matrix from the larger pores, while the fine surface structure appears undamaged, and (as I reported above) a small Aulopora specimen encrusting one side, which was previously covered by matrix.

 

I'm going to soak them again for another week or so. That seems to be the time frame to get discernable results.

 

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ynot

:popcorn:

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Aurelius
On 02/10/2018 at 11:28 PM, Mediospirifer said:

I'm going to soak them again for another week or so. That seems to be the time frame to get discernable results.

 

 

This is very interesting. I've now purchased all of the equipment necessary to blind, scar and poison myself test this on some scrappy fossils. But my main concern is ventilation. Obviously I do not want to breathe the caustic vapour, and I have pets and, to a lesser extent, a wife to think about. I do have a workshop which is separate to the house, with a working ventilation system, but it's designed primarily for dealing with dust and reducing noise to the outside, so there are lots of baffles in the ducting and I'm concerned they'll all end up melted and rotting with deadly toxic vapour. My compressor is also inside the ventilation system, so I'd be concerned that it'd be damaged.

 

The only alternative I can think of is to come up with an animal-proof box which I place outside, and only do it when the dogs and wife are out for the day. Am I over thinking this? Or does anybody have a more intelligent solution? I do have one of those big powerful fans that cannabis growers use (I bought it for use when 3D printing, to avoid filling my lungs with plastic fumes), so maybe I could stick it in the bathroom and use that to vent out the air?

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Mediospirifer

My colleague has been mixing up a beaker of solution (presumably in the fume hood, I haven't been present for this step), adding the rocks, then wrapping the top with Parafilm to get a airtight seal. This seems to contain any vapors. For changing the bath, he first draws a large beaker of water, then slowly pours the solution beaker into the larger container, then rinses the rocks with clean water several times before handling them. The diluted solution can be neutralized with a weak acid (such as vinegar).

 

I took a quick look at soapmaking websites to see what folks who do that recommend for safety procedures. Here's a link to a good site: LINK. They don't say a lot about specific precautions for vapors (beyond that mixing lye with water producers heat and vapors, so use a well-ventilated area), and some of the other sites I found show soapmaking in the household kitchen(!), so I presume a regular window fan above the work area (and an open window elsewhere) should be sufficient. Here's a specific link to KOH safety: LINK.

 

I am planning to try this at home, during warm weather. My plan is to store the material in my garage, sealed with plastic wrap, while it's soaking, and do the preparations and rinsing outdoors, using safety goggles and neoprene gloves. While my colleague is largely unconcerned about the vapors for the amount we're working with, the wet lab here is well-ventilated, and I don't want to take unnecessary chances at home. I also plan to neutralize all of my used solution and test for pH with litmus paper before disposing.

 

I have noticed, after handling specimens that have been rinsed a few times but not soaked in water for an extended period, that my fingertips will feel as if they have soap on them. To deal with this, I wash my hands with lots of water (and soap) until the sensation goes away. I haven't handled anything that wasn't highly diluted, and my fingertips don't seem to be affected in any way.

 

Do you have a garage or storage shed that would be suitable for keeping sealed containers for the soaking?

 

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Mediospirifer

Update on my specimens.

 

At the moment, all of the fossils I've been soaking in hydroxide solution are at home soaking in water. Here's a few observations:

 

-- All of the fossils are coated with a light gray residue after the hydroxide bath. I rinsed them under water last night and used a toothbrush, but most of it did not come off easily.

-- The Devonian corals (both of them) look really clean, except for the light gray residue. Looking at them under my loupe, they appear to be undamaged.

-- The larger (horn) coral developed a dark discoloration on one side in the most recent bath. We don't know the cause of this.

-- The Devonian bryozoan (Atactotoechus fruiticosus) has a patchy look to the residue coating, correlated to how much matrix covered a given part of the fossil initially. Areas that started out clean are now a very pale gray, while areas hidden by matrix are closer to the natural color of the matrix. Under the loupe, the palest areas also appear to be smoother that they were at the outset. Whether this is due to the residue coating filling in details, or to corrosion of the fossil, remains to be seen. I plan to get the residue off, then examine the fossil under the microscope for comparison.

-- The Ordovician brachiopod hash pieces have (almost) completely separated (there are a couple of pieces still attached). Most of the matrix has come off, although there are still areas that could be further cleaned.

-- Like the bryozoan mentioned above, the Ordovician brachiopods have turned a very light gray. I haven't looked at them under the loupe, and plan to put them under the microscope to check for corrosion damage after removing residue.

-- For the latest iteration of the hydroxide bath, my colleague placed the larger beaker in a chemical fume hood with tinfoil over the top. The tinfoil was corroded on one side when we drained the beaker. The fumes from this procedure should certainly be accounted for and respected!

 

A few bits of advice from my colleague for handling this at home. First, use a glass vessel for the bath, not plastic or metal. Lab-grade plastic (Nalgene) can be used for the dilution stage; ordinary household plastics should not be used until the specimens have been soaked through a few changes of water.

 

I'll post further updates when I have more progress.

 

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Mediospirifer

Further updates, after a few days of soaking.

 

-- The residue is slowly coming off. I soaked everything for a few days, with periodic scrubbings using a toothbrush. Some areas of some fossils have come clean, others are still crusted.

-- The dark area on the horn coral, under the microscope, turns out to be the natural surface of the fossil (it looks darker because it's wet). Not a stain after all.

-- The crust can be scraped off using a wooden toothpick or metal dental pick. This is tedious! I may use this technique for removing the last traces, but not for the whole layer.

-- The Ordovician brachiopods appear undamaged under the microscope. I plan to soak another set of them, with microscope photos before and after.

-- On the bryozoan, there is one area that has come clean with the brush. The structure of the fossil appears undamaged (under the loupe; I haven't put it under the microscope since getting the residue off).

-- On Saturday, I acquired an inexpensive fishtank filter and mounted it on the side of a bucket of water, with the corals on a piece of mesh under the outflow. My chemist friends tell me that given enough time and water, the residue should dissolve without harming the fossil. I'm checking it (and scrubbing briefly with the toothbrush) once or twice a day, and the residue appears to be thinning.

 

I have a bag of horn corals for the next bath; I want to get some good "Before" photos before I bring them in to soak. I plan to scrub them to remove residue with each change of solution, rather than let the crust build up unchecked.

 

I'll post again when I have more information.

 

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Mediospirifer

Further update, and a change in plan.

 

Talking more with my colleague, it turns out that he's been soaking my fossils in sodium hydroxide, not potassium. It seems that this shouldn't make any difference, but it may account for the difficult residue.

 

Also, it turns out that I was sloppy in my identifications! My "bryozoan" fossil isn't: it's a coral. I could say that it was too crusted with matrix to tell the difference, but my "Before" photos show the truth. Sigh...

 

The residue-removal progress is slow. I've observed a few spots where small bits of residue have flaked off under the water flow, but this is not an efficient process. A couple of days ago, I tried applying a few drops of vinegar to the residue layer under my microscope, and it doesn't appear to be particularly reactive--I think I saw more gas bubbles develop from the vinegar applied to the bare fossil! (Applied to the broken end of the fossil, not the surface I want to preserve.) Drying the fossil, then wetting it seems to soften the layer a little, so that I can use a toothpick to get some results. It's still tedious.

 

The change in plan: I've brought in a few more fossils (4 corals and 2 bryos--choosing carefully this time!), and Colleague is going to soak one trio in each of the two solutions. After a week, we'll see if there's a difference in how the residue scrubs off.

 

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