Ammonite prep

[holdinghistory]

Just finished up my first Ammonite prep. I had gotten a few of these from RJB a little while back, and finally getting around to them. I forgot to get a complete before photo, so here it is after some initial scribe work. Prepped with a CP-9361 and Aro scribes. Any constructive comments welcome too, this is the first ammonite I have ever prepped, three more to go so any pointers are welcome!

[holdinghistory]

And here are the after photos. 

[holdinghistory]

[Macrophyseter]

Beautiful prep! 

[thelivingdead531]

I’ll second the statement above, beautiful! 

[Bobby Rico]

Very nice indeed.

[Tidgy's Dad]

Excellent work! 

Especially for a first effort. 

They look lovely. 

[Darktooth]

Good job!

[Peat Burns]

Looks great

[caldigger]

Nah, chisel and sledge, it's the only way.

[Ptychodus04]

Great job. The CP9361 will move some serious rock.

 

I find that a light application of very thin PVA to the scribed matrix will darken it ever so slightly. In my opinion, the slight reduction in contrast between matrix and specimen makes some of the finer details pop.

[Bone guy]

those came out well! good job

[holdinghistory]

1 hour ago, Ptychodus04 said:

Great job. The CP9361 will move some serious rock.

 

I find that a light application of very thin PVA to the scribed matrix will darken it ever so slightly. In my opinion, the slight reduction in contrast between matrix and specimen makes some of the finer details pop.

 

Good idea! What proportions do you usually mix the PVA for this (similar to Paraloid B-72? That is what I have)?

 

I am working on getting a chisel point for the CP scribe for more bulk removal, hoping it works well. I have the stock tip right now, works quite well, but has limitations.  

[Ptychodus04]

3 hours ago, holdinghistory said:

 

Good idea! What proportions do you usually mix the PVA for this (similar to Paraloid B-72? That is what I have)?

 

I am working on getting a chisel point for the CP scribe for more bulk removal, hoping it works well. I have the stock tip right now, works quite well, but has limitations.  

Paraloid will mix to the same ratio. I use part PVA to 50 parts acetone by volume. Since Paraloid comes in pellets rather than small beads, you will want to go with a 1:40 ratio by volume.

 

I have been using the stock tip as well but am about to upgrade it to the Paleo Tools stylus since my stock tip is getting pretty worn.

[RJB]

For me, i have never liked the CP9361.  Simply dont like the stock stylus.  If you can get a stylus like the one used for the ME9100 from PaleoTools I think you will be amazed.  But still, nice job on the ammos. 

 

RB

[holdinghistory]

Thanks Ron! I am not crazy about the CP9361 tip either. I have considered replacing it, but I have a few other tools higher on my list first. In the meantime, I picked up a new chisel tip for the CP, but the blunt end just came today in the mail so I haven't installed it yet to see what kind of difference it makes. 

[RJB]

here is what I mainly use.

 

RB

[Ptychodus04]

Paleo Tools makes a conversion kit to allow the CP9361 to use the ME9100 stylus. 

[holdinghistory]

Definitely look like an upgrade versus the CP.

[RJB]

14 hours ago, Ptychodus04 said:

Paleo Tools makes a conversion kit to allow the CP9361 to use the ME9100 stylus.

@holdinghistory,  This is what you need fella.  Good luck

 

RB

[DevonianDigger]

On 4/28/2018 at 11:41 AM, holdinghistory said:

Thanks Ron! I am not crazy about the CP9361 tip either. I have considered replacing it, but I have a few other tools higher on my list first. In the meantime, I picked up a new chisel tip for the CP, but the blunt end just came today in the mail so I haven't installed it yet to see what kind of difference it makes. 

 

That's a really nice bug you've got in the background there! Forget the scribe tips, lol!

[holdinghistory]

Thanks Jay! It is a Megistaspidella triangularis, just came in the mail recently.

[Fossil-Hound]

On 4/27/2018 at 7:13 AM, Ptychodus04 said:

Great job. The CP9361 will move some serious rock.

 

I find that a light application of very thin PVA to the scribed matrix will darken it ever so slightly. In my opinion, the slight reduction in contrast between matrix and specimen makes some of the finer details pop.

Isn’t PVA a cementing agent. Just picked some up. I’ve heard PVC is good. What’s the difference?

[Ptychodus04]

PVA is polyvinyl acetate. Trade names are Vinac B-15 and McGean B-15. It is a stable plastic polymer. Typically for fossil use it is dissolved in acetone and used as a glue or consolidation material. 

 

Elmer’s glue, or more generically white glue, is also formulated from PVA so why is it bad for fossil conservation? The main difference is solution vs suspension. When PVA is dissolved into a solution, it retains all of its original properties once the solvent evaporates, making it a very stable and 100% reversible material. When PVA is used in a water suspension, it behaves differently. Since the plastic doesn’t readily dissolve in water, the PVA is ground into very fine particles that absorb a small amount of water (that’s why it is white and dries clear). When applied to an object, the suspension mostly dries on the surface. The particles bond to each other in a way that makes them very resistant to future dissolution and they will also break down over time rather than remain stable.

 

Unfortunately, all known forms of PVA (B-15) are out of production and are becoming scarce on the market. Suitable (and superior) replacements are Paraloid B-72 (a copolymer of ethylmethacrylate and methyl acrylate) and Butvar B-76 (polyvinyl butyral). Both are soluble in acetone and are known stable plastics.

 

PVC is polyvinyl chloride and is mostly used as a building material. Its base material is toxic and a known carcinogen.