Sieves and Sifters- advice needed

[LabRatKing]

Hello gang.

 

I am looking for advice from more experienced folks about sifting for fossils.

 

I have a wide range of appropriate tools available to me, but as one that has never really done this sort of fossil hunting, I have some questions before my excursion this weekend.

 

I always have a canvas bag/tube type I normally use for forest floor detritus to find various insects and the like. It has also proven useful in streams and creeks. Very handy as it folds flat and doesn't use up much pack space. However it is in the sieve range of #3-4 (about 5mm +/-). I don't know if I should be dragging it up the slopes due to its limited size.

 

I own a number of full sieve sets, from the fancy brass and steel mining types, to the lighter plastic "student sieve sets"  (U.S. Bureau of Standard mesh sizes 5, 10, 35, 60, 120, 230, and a few extras in the micron range) However these tend to be pretty unwieldy to haul around and they are on the small side, being around 200mm in diameter.

 

I also have a set of the large wooden "archaeology" sifters- wooden frames with handles about 45cm by 90cm. The rocker frame is missing, but they were a steal at 5 bucks at an auction. 4 different mesh sizes from about 10mm down to around 2.5mm.

 

Anyway, I was just curious as to what you "pro" shark tooth sifters use, if anything, while out in the field. This comes up as I got to see some very promising photos of some stuff found by other campers at the sites.

 

I'm thinking I should take them all, since base camp is just a few dozen meters from the prospecting sites. and I can easily hike back and forth if I stumble on the dental detritus motherlode or something...

 

I should add that it is going to be a very wet day on friday, and I doubt if things will dry out much by saturday, however the proximity to the "river" makes me think my 5 gallon bucket might be handy to do wet sieving.

[jpc]

since you will be so close... take them all.  I rarely screen in the field, but my areas are so different from the stuff folks do in FL streams.  If there are lot of small fossils in poorly cemented rock, I take a sample of the rock home and screen it there in the lab.  

[Scylla]

The size of your mesh really depends on the fossil assemblage you are looking for. If you are going to a site with 6 inch megs it is very different than a site with 1/4 inch teeth. The screens I used in Bakersfield are very different than the ones I use in the NJ creeks. (In NJ I usually take a screen, leave it in the car and just surface collect the gravel banks) That said, nesting screens can help, but it is most time efficient to pick out the larger teeth from the top screen and just dump the micro material into the 5 gallon bucket to be sorted back at home. Whenever I have tried more than 2 screens it got too unwieldy. If you have the space, take all the screens and try them out at the site. Screens that can sit or float hands free are a huge plus so if you are in water consider a pool noodle float zip tied to the screen and a stick with a short rope to anchor it. Good hunting!

[aplomado]

I use double decker sifters, with 1/4" mesh in the first tray and 1/8" mesh in the lower tray.  The majority of the fossils are caught in the 1/8" mesh!

However, using the 1/4" on top makes it a lot easier to search the bottom tray.  Posters on this forum suggested this to me these ideas to me, I did not come up with this concept.

 

Here my final version of the sifter.

 

Make two wooden frames of identical size.  I used  I used simpson strongtie angles from Lowes to attach the wood parts (Simpson Strong-Tie 2-in x 1.38-in x 2.05-in 18-Gauge Steel Angle).

 

I used 1/4" mesh to one frame and 1/8" mesh to the other.  I nailed wood trim on the over the edge of the mesh to prevent it from cutting anyone and to attach the mesh to the frame.  I added handles to make them easier to carry.

 

The two frames are held together by two "toggle clamp latches", opposite to each other.  These latches can be purchased online from the rainforest store, etc.  I recommend adding lock these toggle clamp latches are nice, because you can easily adjusts the length of the fit of the two frames.  I used nuts and lock washers to stop the toggle clamps from moving out of adjustment.

Edited April 26, 2021 by aplomado

[Scylla]

Are the handles on the top screen or bottom?

[aplomado]

They are on the top, but I don't think it really matters.  Let me know if anyone wants to see better pics.

[NickG]

Those are pretty impressive.

 

On the cheaper and easier end,

I recently banged a set of sieves together, 1/2 inch, 1/4 inch and window screen..I haven't had a chance to try them out yet. The window screen has a 1/4 inch hardware screen under it for support.

 

I hope these pictures help anyone else would like to make something similar.

 

[Ironhead42]

The clasps are a great idea! I am going to borrow it when I build my set.

[aplomado]

I wanted to say that I updated my double decker sifter design to nesting sifters rather than using the clasps.  The clasps work fine for the most part, but having them nest is less awkward in the field.  It is a bit more complicated to make, perhaps.

 

The smaller top sifter is 1/4 mesh.  

 

The larger bottom sifter is 1/8 mesh.  This sifter has four small wood blocks attached to elevate the top sifter so small objects can fall freely through the top screen.  I use a small bungee cord to attach the two when carrying, and remove it at the site.  You don't really need them attached when sifting... I can put my thumb on the top sifter when agitating in the water if I need to hold them together.  The carrying strap is a guitar strap held on with carabiners.  I remove the strap at the site, but it works well for carrying on my back down a creek.

[Ironhead42]

Interesting. I like the nested design better. I think I might put the lifts on the bottom of the upper trays. I think it might be less likely for fossils to get stuck on the lifts this way.

[aplomado]

Yeah, the nested design is a lot better.  I think I am going to try and convert some of my latch-style ones to nested.

[erose]

Another note of caution. Don't make them too big.  After the first few trips to the New Jersey streams I rebuilt mine to be about 16"s square, not 24!

 

It happened to be what was available but I used 3/16" stainless steel mesh and have a window screen insert for little stuff.  

 

PS, one of my best hunts at Big Brook was re-sifting some one else's piles. Found two huge Enchodus fangs and numerous other teeth. that dropped thru someones "large" screen.

[Scylla]

On 11/27/2022 at 7:36 AM, erose said:

Another note of caution. Don't make them too big.  After the first few trips to the New Jersey streams I rebuilt mine to be about 16"s square, not 24!

 

It happened to be what was available but I used 3/16" stainless steel mesh and have a window screen insert for little stuff.  

 

PS, one of my best hunts at Big Brook was re-sifting some one else's piles. Found two huge Enchodus fangs and numerous other teeth. that dropped thru someones "large" screen.

I often search screening spoil piles and find fossils that were long and skinny and ones that weren't recognized like shark cartilage.

[aplomado]

My son found a nice large mosasaur tooth fragment in someone else's spoil pile...!

[Scylla]

On 1/4/2023 at 9:44 AM, aplomado said:

My son found a nice large mosasaur tooth fragment in someone else's spoil pile...!

See?

[aplomado]

I found a pretty good way to carry a double decker sifter and shovel.  A guitar strap on the shifter handles lets you sling it over your back.  A pair of small bungee cords clipped to the handles also holds the sifter together, along with a small shovel.  This lets you keep both hands free when walking down a creek.

Note: the shark design on the shorts is not necessary, but highly recommended.

Edited June 20, 2023 by aplomado