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paleo

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Donnerstag, 17. März 2016, 02:10

Preparation of Koneprusia

Hi all,
I`ll join in, since it`s indeed a bit quiet here lately as Tim says. No one else preping? :205:

Was curious about this little bug, so I started to scribe a bit. Perhaps a bit too much, since all the pieces still need to be glued together and I am not sure yet if it was a good approach to start preping from inside out, so far all good, but will have to wait and see, now comes the tricky part. Plan is to prep all spines freestanding without breaking, but probably too ambitious thinking, hehe, not sure if I can pull it off, it`s worth a try though. In any case a project one can learn a lot from, but will probably take a while before I can show the finished specimen, lots of work, lots of spines and I still need to figure out how to get the rest out. Probably also get a longer nozzle or needle and some softer abrasive before I am ready to finish this project and she agrees to come out. It`s a little Koneprusia from Foum Zugeid. Separation is good as usual for this type of matrix, but the details are tricky to preserve even with blasting. And it would probably take ages to blast it all properly. At least for me, it`s over 30h in this stage and mostly airscribed. :303:

Because of the 2 spines on first two segments my guess is K. dahmani, perhaps any experts here can confirm? Has a nice little surprise also, axial spine on the 4th segment is shorter and thinner as the spines on the 3th and 5th segment. A pathology, or maybe not? You`re welcome to share any advice or tip that might help also. Or if anyone knows anyone (in EU) that sells or has too much of abrasives, softer than iron powder, which is a bit to agressive for this type of work and could sell a kilo or two or more, that kind of tip or help would also be appreciated. :096:

Cheers, Alex
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Fred

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Donnerstag, 17. März 2016, 11:41

Hey Alex,

Seems like you're doing pretty good so far. I believe it's a good idea to keep the pieces apart for the time being, this gives you much more room tom maneuvre. But it will complicate the job of gluing them back together.
But you'll do fine.

What's the grain size of the iron powder you're using? The 'agressiveness' of blasting media is influenced by the grain size, a.o.
Compare hitting someone with a billiart ball, or a bowling ball. Both will hurt, but the bowling ball will hurt more.

paleo

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Donnerstag, 17. März 2016, 12:56

Hi Fred,
yes keeping the pieces apart as long as possible was the idea. It is already tricky to prep between all the spines withouth a longer needle, when all glued back it would be even more complicated, so trying to prep as much as possible before transfering the "negative" back, but as you say it might complicate the job of gluing. Also, might be better to look for spines which are curved-in from outside, a reminder to keep in mind for next project like this. What I am not sure at this time and have doubts that I scribed too much already, is in regards to cleaning the spines from both sides before sandblasting matrix bewteen the spines, probably a good idea, but could prove tricky, since there will be not much matrix left from the inside to support them.

I am limited with grain size of iron powder at the moment. Grain size is around 40-70 micron; mostly around 50 micron I think, cant`t sieve it to more uniform size atm. Works well for pleura, but not for delicate details such as spines, it will burn the skin on spines even at lowest pressure. A softer powder works better as far as I can tell from a small sample I was able to try, probably also smaler grain size would help as you say...

Cheers, A.

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Donnerstag, 17. März 2016, 13:22

50 micron is already very small...
What kind of powder was the small sample you're talking about?

Michael

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Donnerstag, 17. März 2016, 14:33

Hi Alex-

I´m fascinated by your project, wish you all the best for further preparation. For me it´s always magic to see how you guys free such thin spines out of hard stone... I´m curious to see more of this trilobite, wish you a calm hand and very good eyes.

Best wishes
Micha :014:

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Donnerstag, 17. März 2016, 15:10

Hi, all!

Thank you Micha!
50 micron is already very small...
What kind of powder was the small sample you're talking about?
CaMg(CO3)2. It`s a little trilobite, about 3+ cm long, so fine details are quite delicate, smaller grain size as 50 my could work even better, I think... As you say, it`s as hitting the skin with billiart balls... You can see how iron powder even at this grain size at low presure starts to peel the skin off spines and color changes. Dolomite seems to work less agressive, but still tricky to preserve smallest details and even here you can see how it starts to effect the surface, if not careful.

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Donnerstag, 17. März 2016, 16:41

Interesting. The Dolomite I have (I'm not sure about the grain size, it's likely mixed) behaves a bit more agressive compared to my 45 micron iron powder. As far as I understand it, there's a fair deal of variation in iron powders, depending on the carbon content.

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Donnerstag, 17. März 2016, 18:54

Probably there is fair deal of variation in powders, yes, different percentage of purity. A lot also depends on tank orifice size and nozzle size I think. A large orifice lets more (or larger sized particles) powder into the mixing chamber, so more billiard balls per second... A smaller orifice will let less powder into the mixing chamber, but a small orifice combined with too large nozzle lets more air out, so more kinetic energy at impact aswell, more damage to finest details.

The type of dolomite I have tried seems to be around Mohs 3-3.5, seems
softer as iron (5-5.5 Mohs) and shatters in tiny pieces on impact. Not re-usable! It`s not as pleasant to work with as iron
powder neither; produces a lot of fine dust in the box and flow is also more consistent with iron powder.
Hard to sieve also, tends to clump up. Sandblasting as far as I have experimented with it shortly seems fairly complicated technique and each matrix can behave a bit different, so best to experiment on each project, it helps, but results are probably never as good as with scribe only, so most of the work even on this specimen was done with fine needle so far, but there again vibrations and micro cracks might prove problematic in the final stage.

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Donnerstag, 17. März 2016, 19:12

Hi Alex,

Great job you are doing, pictures show stunning details and a superb preservation. :117:

I’m bit surprised your dolomite is more aggressive than ironpowder. Like Fred I seem to have less abrasive iron.

Keep up the good work

Peter

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Donnerstag, 17. März 2016, 19:38

Hi Peter,
well, perhaps my iron powder is not pure, got it off ebay so not sure where it`s from and since I`m relatively new to blasting (just read the manual and did a bit experimentation on 4 other projects, hehe) I can`t compare it to other iron powder. Seems to work well with harder matrix. Could also be that I have to run it through a few more times so that the edges round a bit more, donno.

Will try with another batch of iron from a different source, perhaps you can recommend any?

Fred you mentioned you are using 45 my iron powder, did it come in larger grain size, up to 100 or 150 micron and you sieved it through or is it available in that size aswell?

Thanks! Cheers, A.

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Freitag, 18. März 2016, 12:41

Hi Alex,

cool project and discussion. Your work already looks very impressive, you preserved the details and original color of the shell. We see a lot of Koneprusia's burned by aluminium oxide and becoming grey and nearly smooth in the process. But keepin mind chiseling is the best way to keep the shell in original state but when it comes to the vertical spines chiseling produces shear force which causes easily hair fractures into the spines. When you try to blast the spines later they tend to break then. I know from discussions with other preparators that grinding is often uses to provide as less as shear force possible by using a tiny diamond sphere head.

And you should not work too long with all the pieces not connected. It will become more and more difficult after more matrix removal to glue all back into the right position.

Koneprusia is a nightmare trilobite for prep-work, but the results you show are stunning and I hope you manage to get the spines freed. But the more spines are free the easier it is to damage them by any wrong move. I think most Moroccan preppers break the spines and reattach them, but anyone who did that will learn how difficult it is to fix such a spine later and find its original position.

Maybe we need custom made nozzles for such works. The Americans love to use nozzles with a very tiny opening, I think they are now back to a diameter of only 0.2 mm and that's works only with a homogene sieved dolomite powder which is expensive to get.

All the best and I'm off for some days. Stuttgart is calling.

Jens
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Freitag, 18. März 2016, 16:49

Hi all,

Jens, thank you for the info! Indeed, it is a problematic bug; skin is good preserved (except for the edges of negatives, which seem to be weathered, so spine tips might be more problematic) and matrix from Foum Zguid as usual fun to work, project starts easy, but it quickly becomes tricky and the degree of difficulty progressing with more bug free. Just the contrary as when working on non-spiny species. The details are just so small and fragile to preserve and spines closely packed, so not much place to work. It started as an experiment, will see how it will end, you can do your best, but as they say "first one is always a throwaway." ;) :199:

Best way to preserve the shell is really just needle work, there is tiny micro granulation present between the tubercles, thorns and spines, all over the body, on spines, cephalon, pleuras. Thorns on first 3 spines curve up like thorns on a rose and these are also mostly "robust" enough to be preped free withouth blasting. I try to work with vibration to the minimum, except for landscaping no strong tools used. Not sure if grinding would bring much less vibrations; only safe way would be to blast it all and even then spines could break, I guess. I expect more problems near the end, will definitely not go withouth breaking some spines in the process, but I plan to try to avoid breaking on purpouse, since I know it`s not fun to glue them back in place.

A small update... These cyphs have been following me on last few projects and guess they still like me. :) To bad it`s cephalon only and the rest of the pieces shatered allover the place. Will probably remove it, not sure if it would look good and it would probably complicate prep even more. Thinking about how these fossilized and debries you usually find when preping, it`s almost a miracle that Koneprusia is found with spines in place.

Cheers, Alex
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Freitag, 18. März 2016, 17:18

Wow Alex, :014: nice work so far.
Yes that Cyphaspis isn't in a good place there. That won't be easy to avoid.
Nice details. I'm looking forward to see more of this piece.

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Freitag, 18. März 2016, 18:24

Hi Tim, its very close, hopefully the spines of Koneprusia on this side are not broken already. If Cyph was more complete I would try to prep it, it could be done, but would see more of it in crossection then probably, it was a surprise and is a partial only, pleural segments after cephalon are missing, found the 6th segment with spine isolated next to the cephalon on left side and a few mostly isolated and shattered allover, destroyed a few while landscaping matrix already... It`s nice to see they are found in same layers however.

Cheers, Alex

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Montag, 21. März 2016, 08:46

Hi Alex,

i am following this topic with great attention. You have a hell of a challenge ahead and i look forward to see the different techniques to be used to free this fellow from his matrix.

Anyway i wish you a steady hand.


Best regards

Luc
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Dienstag, 29. März 2016, 23:47

Hi all,
thanks Luc, I will definitely need a steady hand now.

An update. About 90 hours in the prep now. All pieces transfered in place, hopefully they stay there and I don`t have to glue them again. Glueing part was a mess... I had a feeling that glue set-in to quickly and that I was not able to get a perfect fit, while cheeking the occipital lobe/spine base, so I decided to remove glued parts with acetone, make a larger window and try again. A mistake! You can imagine how that went... Ironically on second try it turned out a bit of shell was lost there when rock was split, so removing it the first time was probably a mistake, was probably just as good fit the first time, but with less broken parts. Anyway, managed to clean the mess with excess glue, but not fun and time-consuming. :303:

The rest went more or less well so far, I guess. As you can see I decided to transfer the drifted librigenia closer to original position, I like it much better this way, although it`s not really the natural prep approach, a bit too close and risky aswell, but came out nice. When I find more time the tricky part starts. I can tell you already, it doesn`t go without breaking a few spines, but hopefully nightmare doesn`t start now.

Cheers, Alex
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Mittwoch, 30. März 2016, 00:24

Hi Alex,

woah, looks already great. But now it's the time where every move has to be correct. Any clumsy action and you will start to cry. Hope all went well. These spiny bugs are nerve-wrecking and there is a reason why I didn't started a Koneprusia recently. Looks really great, fantastic shell details.

all the best and a calm hand.

Jens
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Mittwoch, 30. März 2016, 00:41

Thanks Jens! Indeed, the problems might start now. I`m more worried about secondary spines, especially about pygidium that has microcracks (hammer hit stone there), though. Preping the spines free would be a lot easier withouth trying to preserve those, I`m not even sure how some prepers are even able to preserve those almost fully and freestanding. For example Hammi`s masterpiece we discussed some time ago, that seems like magic, if it`s done in same type of matrix/shell preservation, perhaps better in softer matrix, but even then... Anyway, thanks!

Cheers, Alex

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Mittwoch, 30. März 2016, 10:55

Alex, stunning results so far! I wish you a steady hand now, you're going to need it. :201:

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Donnerstag, 31. März 2016, 05:27

Wow Alex, that looks already amazing. What a nice deatail on the cephalon.
This is already a stunning result. Can't wait to see how you are going to finische him.
Good luck.