Win a copy of Keeping Bees with a Smile this week in the Honey Bees forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education skip experiences global resources cider press projects digital market permies.com private forums all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • Mike Haasl
  • Anne Miller
  • Joylynn Hardesty
  • Pearl Sutton
  • paul wheaton
  • r ranson
stewards:
  • James Freyr
  • Devaka Cooray
  • Jocelyn Campbell
master gardeners:
  • Steve Thorn
gardeners:
  • Ash Jackson
  • thomas rubino
  • Jay Angler

How do I determine the silt to clay ratio in my soil sample?

 
Mark Maitland
Posts: 2
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I conducted several soil sample tests per Earthbag Building by Kaki Hunter and Donal Kiffmeyer. I wasn't sure how much silt vs clay is in each sample. Should I separate the sand and rocks from the mix then test the finer suspended materials? There is a pretty good indication that I have a some silt and some clay due to the stickiness and slipperiness. I guess I just want a little more assurance of what the clay vs silt ratios are. Thanks for any suggestions.
-Mark
 
Joseph Lofthouse
steward
Posts: 5104
Location: Cache Valley, zone 4b, Irrigated, 9" rain in badlands.
1818
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

A soil particle profile test is conducted about like this:

Put some soil and water in a jar. Shake the heck out of it.

Put it aside to settle. After one minute put a mark on the jar at the top of the sediment layer. This is the top of the sand layer.

After 2 hours put another mark on the top of the sediment layer. This if the top of the silt layer.

Wait for however many days it takes for the water to become clear. Put a mark on the top of the sediment layer. This is the top of the clay layer.

Measure the height of each layer. The percent silt would be the height of the silt layer divided by the total height of sediment.

Likewise, the silt/clay ratio would be the height of the silt layer divided by the height of the clay layer.
 
Jay C. White Cloud
Posts: 2413
46
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi Mark,

To add to what Joseph already shared, remember that soil "jar tests" are very, very basic guidelines of what a soil is presenting with. Many forms of silts and clays can have similar characteristics to one another...both in the jar and in the hand when physically testing them. Some silt will act almost exactly like a clay, and can be very deceiving. Without in depth soil analysis under a microscope and with the trained eye of a geologist or someone with similar training, we can only get a "guess" at what a soil has in it by the "jar test," and that may be more than enough in most applications.

If building with your samples, then I would strongly advise building "test block" and even a "test wall section" to better understand the load dynamics of a cobb type or related mix. Most states have "soil testing" for free or little money and this is also advised to take advantage of. Local universities will also often do this and even let you watch and learn something along the way...it can be really fun for younger members of the family as well and something they can share with others in school...

Something I have be meaning to add to one of these post about "jar test" is the subject of:

Sedimentation Principles

Sedimentation, for example when a river may slow in its course and form impoundments like "oxbow lakes," which is nothing more than a big bend in the old river, these rivers (moving water) slow and have less energy. With decreased energy, "sediment capacity" is dropped, and with it the "dropping of sediment." The first particles to settle will be the largest - the sands and gravels. This is one reason levees are built with sand as are other "emergency" structures are built with sand...or sandbags. The second largest particles are silts. Alluvial plains at the discharge point of many rivers is composed of silts. In many rivers if we put a sample in a jar to sit for a few hours, we would have a layer of soil appear on the bottom. Other than any sand that may have settled out quickly, this layer is composed of mostly of silts.

The third and smallest particles are the clays. Clays have a very weak electrical negative charges on their particle surfaces. They virtually never settle out of suspension, because of this characteristic, and being light structurally for their small particle size, plus they repel each other from having that like surface charges. Even if we put a sample away for an entire year, there are clay particles still in suspension. Depending on turbidity (agitation of jar sample) some clay types could actually take as long as 1000 years or more to fully settle. This reason alone, among several, is the reason the "jar test" is not overly reliable for testing clay types and qualities alone. Some (many?) clays will attached to silts or be trapped with them.

Regards,

j
 
Don Benham
Posts: 2
Location: Central/Northern Virginia, USA
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Great information. 1000 years huh?

What University department would I contact?
 
Jay C. White Cloud
Posts: 2413
46
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi Don,

Any college, even some junior colleges, with a geology/soils department. Agriculture colleges can do this too. You can call first, but I like (when new to an area) to go in person. It helps them understand better why I need the sample tested. I know longer have a good soils microscope, but getting one and learning to do your own testing isn't a bad idea if working with a great deal of cobb formulations...

Regards,

j
 
G Moffatt
Posts: 29
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
mark your total on the jar before adding water. I used to be a materials inspector.
 
Jay C. White Cloud
Posts: 2413
46
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

G Moffatt wrote:mark your total on the jar before adding water. I used to be a materials inspector.




Hi G.M.,

I will stress again for our other readers that "jar tests" are exceedingly inaccurate, and should only be used as a very rough guide...at its absolute best. It should also be noted that some clay soil types with certain silt types in many areas will give a "false read" for the clay percentage.

If I am understanding..."mark your total on the jar before adding water"...I agree...As the "dry soil" level does need to be recorded (as point reference) before adding water. However, there are more steps after this...Joseph Lofthouse indicated above...

 
Terry Ruth
Posts: 698
26
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I agree with the Jay the jar test is basic and not detailed enough. I got a little story about University Geology departments....I tried to get them to network with me about six months ago to help reinvent the building wheel to natural locally from the design to testing a live build with students involved..... and the Professor that taught the class never called me back after he said he consider it. I told them it could make local news and it be a great learning experience for students and us. I also tried to get some CAD drivers from another University in my network to do the modeling, no luck. Then I tried to get code adoption, long battle. So hopefully others have better luck then I did. I'd suggest not leaving the decision up to the Professor of the class, go to the Dean then the Professor will have to abide. After I thought about it a while I decided to take all the glory heck with them and keep my mixes proprietary Plus the liability and insurance issues for both us and the university may be why I never got call backs. The lab test are not that expensive and well worth the $$.
 
Eivind Bjoerkavaag
the navigator
Posts: 89
13
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Roll a sausage between your hands and bend it. Is it bendable and you can form it, it is rich in clay. If it doesn't bend much before it snaps then it is rich in silt (if your glass test was difficult to read).

Nice test to do if you are out and you are unsure wether the small particles are mainly clay or mainly silt.
 
Barry Frantz
Posts: 2
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
If you know where the sample was taken, and how deep it was taken, you could use USDA-Natural Resources Conservation Service (NRCS) soil survey information that includes data about sand silt and clay. available on "web soil survey" at http://websoilsurvey.sc.egov.usda.gov. it may not be the exact sand silt and clay ratio of your particular soil sample, but unless you really need to know the exact percentages for some reason is probably a more accurate average number than what you will get by trying to test it yourself.

the finger roll method is a pretty good quick method, BTW
 
Their achilles heel is the noogie! Give them noogies tiny ad!
How to Make Your Own Emergency Home Battery Bank
https://permies.com/wiki/38548/Emergency-Home-Battery-Bank
reply
    Bookmark Topic Watch Topic
  • New Topic