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Made this quick reference guide as a fun little graphic to aid in sandblasting matrix.  Hopefully, someone finds this useful! Enjoy!

Vaniman Material Hardness Quick Reference Guide. (1).jpg

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holdinghistory

Interesting, thanks for sharing this. Has anyone here tried glass beads? I am curious if you can get them fine enough, never thought to check into them. If you can get the right fineness, it sounds like a possible inbetween before resorting to aluminum oxide. 

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Iron powder is the typical medium over here in Germany and it's not even listed on the left. Nevertheless, thanks for posting.

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@holdinghistoryI am currently awaiting some specimens to test on using a myriad of media's (one of them being glass beads).  Due to the large variability in sandblasting, attributed to technique, device, and so on, my goal is to create a proper reference for new and experienced preppers alike. Of course, one of the challenges with using micro-abrasives is understanding the media. Shape, in particular, is of concern because that will dramatically affect how the blasting surface will react.  For example, Glass Beads, are spherical which cause a "peening" effect.  You can still use it for material removal however its like trying to chop wood with the back of an ax-head rather than the sharp side so the beads are more effective at polishing and making things shiny. 

 

@Ludwigia thank you for the input!  I decided to throw iron on the right column for more of an "ore" like perspective since, in my experience, iron is less used here in the States.  I will be getting a sample however and will be testing using 80um powder.  I'll update when I have some data :)

 

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I wonder why the Germans use iron powder and we use dolomite and bicarb mostly.  Any thoughts...?  

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4 hours ago, jpc said:

I wonder why the Germans use iron powder and we use dolomite and bicarb mostly.  Any thoughts...?  

No idea. I guess it's just a habit that gets passed on. I'm happy with the iron anyway and have never had the urge to try anything else.

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caterpillar

Maybe there are a lot of pyritized fossils in Germany like toarcian ammonites and iron powder give good results on them

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1 hour ago, caterpillar said:

Maybe there are a lot of pyritized fossils in Germany like toarcian ammonites and iron powder give good results on them

That's true, but that's not the reason for using iron powder generally.

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Wrangellian
On 3/21/2018 at 11:17 AM, Vaniman said:

Made this quick reference guide as a fun little graphic to aid in sandblasting matrix.  Hopefully, someone finds this useful! Enjoy!

 

I'm not a prepper but I think I would find this easier to use if you'd arrange those tables with the numbers in increasing or decreasing order, rather than ramdom. Also, the dates on the timescale are a little out of date (so to speak).

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5 minutes ago, Wrangellian said:

I'm not a prepper but I think I would find this easier to use if you'd arrange those tables with the numbers in increasing or decreasing order, rather than ramdom. Also, the dates on the timescale are a little out of date (so to speak).

I agree. 

 

I'm not sure why the geologic periods are there as they seem a bit out of place, or perhaps just tangentially related? :headscratch:Is there another information table that deals with prepping specifically that could take its place? I'm not sure I've ever sat down to prep a fossil and said to myself, "if only I knew which geologic period this came from, it would improve my prep." The other three tables are quite useful, though. :) 

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Wrangellian

I wondered that too but wasn't going to say it... Maybe just a space filler until something more relevant is found?

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36 minutes ago, Wrangellian said:
On 3/21/2018 at 12:17 PM, Vaniman said:

 

I'm not a prepper but I think I would find this easier to use if you'd arrange those tables with the numbers in increasing or decreasing order

Thats the first thing I thought too. 

 

RB

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On 22 March 2018 at 5:12 PM, jpc said:

I wonder why the Germans use iron powder and we use dolomite and bicarb mostly.  Any thoughts...?  

 

"Air abrasion" is not an especially good term to describe how air blasters really work. The main effect of an air blaster is not grinding away the matix - it is creating small fissures by hard impacts,  hitting away the matrix. Of course, Mohs hardness is also important, but it's not the only important parameter. If it would be only grinding away the matrix, aluminum oxide (often called alumina) with such a high Mohs hardness (9 - diamond has 10!) could not be used at all!
The impact energy of particles onto the substrate is the main effect to create small fissures and to break the matrix apart and hence the density (mass of individual particles) of the "abrasive" is very important. Iron has a much higher density (7.8g/cm³ for iron versus 2.7g/cm³ for carbonate); at the same particle size, the impact of iron powder is more severe (The impact energy is proportional to the mass multiplied by the square of the velocity ! ), so you can work at lower air pressures. Soft iron powder (not from carbon rich steel) has a Mohs hardness of only 4 to 5; slightly higher than that of calcite or calcium carbonate (3) and dolomite (4) but much softer than that of aluminium oxide (9). 

The particles are also round, hence the powder will flow quite easily. The particles are ductile and do not burst on impact (unlike calcite or glass beads),   you can recover and clean  the blasting media quite easily with a magnet.
Do not confuse soft iron powder with ordinary iron powder made out of carbon rich steel which is much harder and will give quite poor results.

Soft iron powder is an extremely good "abrasive" for very delicate Bundenbach fossils such as this Mimetaster:

Thomas

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Sagebrush Steve
1 hour ago, oilshale said:

 

"Air abrasion" is not an especially good term to describe how air blasters really work. The main effect of an air blaster is not grinding away the matix - it is creating small fissures by hard impacts,  hitting away the matrix. Of course, Mohs hardness is also important, but it's not the only important parameter. If it would be only grinding away the matrix, aluminum oxide (often called alumina) with such a high Mohs hardness (9 - diamond has 10!) could not be used at all!
The impact energy of particles onto the substrate is the main effect to create small fissures and to break the matrix apart and hence the density (mass of individual particles) of the "abrasive" is very important. Iron has a much higher density (7.8g/cm³ for iron versus 2.7g/cm³ for carbonate); at the same particle size, the impact of iron powder is more severe (The impact energy is proportional to the mass multiplied by the square of the velocity ! ), so you can work at lower air pressures. Soft iron powder (not from carbon rich steel) has a Mohs hardness of only 4 to 5; slightly higher than that of calcite or calcium carbonate (3) and dolomite (4) but much softer than that of aluminium oxide (9). 

The particles are also round, hence the powder will flow quite easily. The particles are ductile and do not burst on impact (unlike calcite),   you can recover and clean  the blasting media quite easily with a magnet.
Do not confuse soft iron powder with ordinary iron powder made out of carbon rich steel which is much harder and will give quite poor results.

Soft iron powder is an extremely good "abrasive" for very delicate Bundenbach fossils such as this Mimetaster:

Thomas

That’s a good explanation for how baking soda with a Mohs hardness of 2.5 can remove much harder matrix.

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