Hi HB - as discussed previously, you have to think in terms of what the ERH of your treated rice is, and what ERH you need to preserve your bows at your desired moisture (or performance) level.
I have absolutely no experience of using rice as a desiccant, but hey
it has been done. Apologies if this is old news to you. I would assume that your treated rice would have a lower ERH than the figures given here, but without measuring you’ll never know for sure. Also, on no reasonable basis whatsoever, I would guess that the “response curve” (as previously discussed) would be relatively flat compared to most commercial desiccants.
Based on the wood moisture tables it appears that white rice will settle in at about the same moisture levels as wood. What I like abut it is I am able to cook off the water and determine MC% so I could safely say my wood is heading for the same number if given enough time. Untreated rice would not be nearly as effective I am sure.
HoneyBadgerDC - I am still convinced that the use of strain gauges and a strong Dessicant will give you the best results. There are lots of variables in this and a direct measure of bow strength (the strain gauge method) is your best option.
I think I am agreeing with you on the stronger desiccant. One of the problems with a strain gauge is that maximum strength and stiffness in tension don’t go together. At about 6% moisture most woods will became weaker in tension meaning they will fail sooner but still may test stiffer. Not much elasticity on the tension side so it could get very risky. 6% is pushing it. I don’t know how to test it for failure without actually breaking the bow. Working with natural material bow strings we always do break tests on the strings to determine how many strands we will need as a minimum. Moisture levels of the strings has a huge effect on the breaking points, the get stronger as moisture goes up which is the opposite of the compression side of a bow. It is mainly the compression side we are trying to manipulate without compromising the tension side too much.
This is an aside to the bow discussion but at NASA we had a “dry room” similar in look to a “clean room”. Tight construction, special air flow system, a protocol for using the room, etc. I believe the relative humidity could be set as low as .5 percent, basically as low as possible. I’m not familiar with the design but I do know it used desiccants as the final stage of drying the air. The desiccants needed to be regenerated every so often so there were parallel paths so air flow could pass through one set of tanks while the other was being regenerated.
Rooms like this were standard equipment for experimental work on battery systems, for instance.
I am starting to think my best option is to simply store them in a 30% to 35% RH at 70 degrees ( room temp)
Something funny about the rice. I made an assumption when I pulled the rice out of the oven that it was likely at about 1% MC, when I weighed it again the next morning I had lost an additional 6% during it’s cooling off period so this tells me I really have no idea how much moisture it actually had. I took off a total of 16% moisture so it seems to settle in quite a bit higher than wood. I plan to check it daily to see how much and how fast it gains back moisture. The first day it gained back 2%. I have a new humidity gauge coming today but I suspect my indoor humidity is about 50%.
I was afraid that was the case but didn’t want to dampen your enthusiasm.
Moisture content is very unintuitive. For example toothpaste has around 30% water and sun dried wood has around 40%.
Also some of the moisture is bound to the molecules while others are not. If you get too aggressive in drying by raising the temperature, you can start pyrolysis.
I am having fun working with this rice. I monitor the weight daily. It responds very quickly to changes in humidity and seems to match the wood moisture charts almost identical to wood. I feel confident that simply going by the charts and allowing enough time to stabilize will be all I need to do. Next I need to find out how much time is needed for a bow with a finish on it to stabilize.
I was afraid that was the case but didn’t want to dampen your enthusiasm.