Variance in Times Pulling Vaccuum with Cactus Juice

[jeporter02]

Trying to understand the science behind this: I had one large piece of cherry burl that I cut into two smaller pieces to stabilize and cast. The first piece I dried in the oven for 24 hours to as near zero water content as I think I could get. I put the hot piece of wood in a Ziploc bag overnight to cool. I submerged it in Cactus Juice and pulled a vaccuum. Bubbling continued in the Cactus Juice for about 12 hours before slowing to a pace that I felt good removing it from vaccuum and then curing it in the oven. About a month later, I took the second piece of the same burl, dried it in the oven for 24 hours. I took it out, weighed it, and it was 380 grams. I put it in for one more hour, and it came out the same weight, so figured I was close to zero water content. I put the warm piece of wood in a Ziploc bag, but it sat there for over a week. When I finally had time to put the dried wood into Cactus Juice, I took it out to weigh to see how much water it had absorbed. Oddly, it weighed 372 grams, so somehow it lost 8 more grams of weight in the Ziploc bag (there was no moisture in the bag). I put the wood in the Cactus Juice and pulled a vaccuum. This time, the second piece of the burl only bubbled for about 3 hours before it nearly stopped bubbling altogether.

So I'm curious: what would have caused the two pieces of wood to require such vastly different times in the vaccuum chamber? They both came from the same burl, both were dried in the oven the same amount of time, but the second piece was in a Ziploc bag for a week, where the first piece was only in the bag overnight. Why did the second piece lose an additional 8 grams of weight inside the plastic bag? Any idea what could have caused this? I'd love to find a way to reduce the wear/tear on my vaccuum pump or not have to run it overnight if possible.

 

[derekdd]

Very interesting. I'm surprised to hear it continued to bubble under vacuum over 12 hours.

I've got no firsthand experience with this process though I plan on getting into it this summer. The guys I watch on YT seem to get all the air out of pieces within 2-4 hours then leave the wood overnight soaking in the CJ before curing in an oven.

Have you verified your oven temps with a laser thermometer and verified the accuracy of whatever scale you're using?

 

[ed4copies]

To me (I ain't no expert) the most important number is missing. What percent of weight did the wood gain after stabilizing?
I always hope to achieve at least a 50% weight gain on cherry. (Weight when finished/weight when put into stabilizing fluid minus 100%=
Weight percentage gain)

As for how the time needed could be so different: What was the ambient humidity in those 30 days between batches?
If it was getting drier as the season changed or if your heating-cooling system was reducing humidity in that time, the wood started
out drier.

 

[1080Wayne]

In my opinion , Ziploc bags are fine for overnight storage , but shouldn`t be relied upon for long periods . The seal may not have been fully closed , there may have been a small hole in the bag , or a bit of foreign material may have prevented the seal from closing at some point . Bag quality varies with bag size . Small bags are made of thinner film . Some have a double seal . I use ones that are about 10x10 inches with a double seal .

That said , I would not have expected 8 gms of moisture to cause that much difference in bubbling time . Even though they were from the same burl , I wouldn`t be surprised at the pieces being somewhat different . I , also , am not an expert .

 

[jeporter02]

Very interesting. I'm surprised to hear it continued to bubble under vacuum over 12 hours.

I've got no firsthand experience with this process though I plan on getting into it this summer. The guys I watch on YT seem to get all the air out of pieces within 2-4 hours then leave the wood overnight soaking in the CJ before curing in an oven.

Have you verified your oven temps with a laser thermometer and verified the accuracy of whatever scale you're using?

I average 10-12 hours on most of my wood, and that's after 24 hours in the oven. I've seen the YT guys run their vacuums for 2-4 hours as well and always wondered how they managed to finish so quickly. This last piece that only needed 3 hours was a surprise. My pump is pulling well over 3000 so I don't think it's a matter of having a more powerful pump. I always let burl soak in the Cactus Juice for a day, sometimes 2-4 days if it's redwood or particularly punky. Maybe that's overkill, but I'm not usually under time pressures and it doesn't seem to hurt anything. I've had great luck thus far…

 

[jeporter02]

To me (I ain't no expert) the most important number is missing. What percent of weight did the wood gain after stabilizing?
I always hope to achieve at least a 50% weight gain on cherry. (Weight when finished/weight when put into stabilizing fluid minus 100%=
Weight percentage gain)

As for how the time needed could be so different: What was the ambient humidity in those 30 days between batches?
If it was getting drier as the season changed or if your heating-cooling system was reducing humidity in that time, the wood started
out drier.

I'm letting the wood soak overnight. Once it's done curing I'll share the percentage gain. That's helpful info though on ratios. Thanks!

 

[its_virgil]

Oven temp
In the oven until the weight stops changing