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Clay slip in straw bales

 
Tom Connolly
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Up until now, the only use I have seen for clay slip is by using infill, i.e. coating loose straw and stuffing it into some kind of pocket in the wall of a house. Has anyone read about - or better yet, done themselves - considered taking the cut straw from the field, coating it with clay slip and then baling it? It would add one step to the process and slow down baling but I like the idea of using a full bale instead of stuffed straw. Also, all of the pics I have seen of houses with straw infill seem to have a lot more framing (wood - more $$) than the pics I have seen of post and beam houses using full bales. Maybe a good question to ask is whether or not a straw baler would tolerate the clay slip? From the websites I have seen that offer a more exact recipe (more than just "add a little" or "add some", it seems that a cup, or a little more than a cup of slip is actually used for one bale of hay. It certainly means more work but the "consensus" is that straw coated with clay slip is more durable than just straw alone.
 
Jay C. White Cloud
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Hello Tom,

Has anyone read about - or better yet, done themselves - considered taking the cut straw from the field, coating it with clay slip and then baling it? It would add one step to the process and slow down baling but I like the idea of using a full bale instead of stuffed straw...Maybe a good question to ask is whether or not a straw baler would tolerate the clay slip?


I have seen similar things to this Tom, with trying to modify a cotton baler to no avail with a paper pulp material. I have several "tractor and bale harvester" collectors around me here in Vermont that we have had similar discussions about. These machines all need a reasonable degree of "care and concern" to operate, and none like "wet hay" or straw, and clog rapidly or "misbehave" more when the hay/straw is too damp. Perhaps a modified or specially designed/built machine could accommodate a slurry of clay slip and straw mixed together before the baling process begins, but thus far I haven't seen any that tolerate the moisture. I know there are "cane balers" and these have to tolerate moisture and sticky, so perhaps could be modified to handle the thinner stalks of straw? I haven't seen anything like this yet other than the small "brick molds" that have thus been discussed in some of the other post conversations around this subject.

Also, all of the pics I have seen of houses with straw infill seem to have a lot more framing (wood - more $$) than the pics I have seen of post and beam houses using full bales.


I believe the wood cost challenge could be inhibitive, as suggested, in some areas, like I am finding in parts of Texas, yet in most builds these are not going to be the heavily processed studs bought at a local box store, but from a local custom sawyer. If they exist around an area the wood cost is not as challenging. Currently in New England, for example, and many areas on the East Coast, this type of stud framing can be purchased for as little as $0.40 to $0.55/ board foot. Even with Timber Frames, or Post and Beam structures, there will be a need for either cobb or wood partitioning walls between rooms. These indeed are an expense "added" to a structure, which some mitigate by having as few these as possible or making them very lightweight, such a Fusuma or Shoji style walls, though this does lower the positive effect of "thermal storage and dampening" by these mass walls and does not address issues with sound transmission.

It certainly means more work but the "consensus" is that straw coated with clay slip is more durable than just straw alone.


The more builds there are, and the more time we have to compare the two modalities, or walls that are cobb mortared SB, the more I lean away from SB (accept in dryer climates) and more towards Straw Clay Slip (SCS) as a better alternative to the SB in general. I still like SB, and think in the hands of experienced design/builders they present as having a very positive application even in some rather humid areas, but I don't think of these as DIY first or second time builds is something I could ever recommend. The "forensics" coming back each year on many DIY builds of SB or similar type roughly seems to be in the range of 50/50 when it comes to overall performance with no major issues. The primary challenge seems to be rooted in "interstitial moisture" within the bale, that can go unnoticed for a long time, general dampness, and plaster failures (typically related to the moisture issue.)

For other readers, this Post has similar content to this conversation:

Dipping straw bales into a clay-water mixture.
 
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