Should CA Steam and Bubble?

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goldendj

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Preparing some spalted tamarind I bought when first starting, when I didn't understand the difference between spalted tamarind and *stabilized* spalted tamarind. I was worried about it breaking up as I drilled it so I figured I'd soak the ends in thin CA. Imagine my surprise when the it started smoking and bubbling like mad ...

Eventually it settled down, and drilling went successfully, but I was wondering if that was normal.
 
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Stabilization generally refers to a process where all of the water is removed from the wood and then the wood is saturated with a liquid resin that is then cured. Water helps to initiate the CA polymerization, unstabilized wood has a lot of water in it. Thin CA will react very quickly at times, the fast reaction generates heat which then causes the reaction to proceed faster, the heat generated can boil the water/CA and generate bubbles and vapor. This tends to happen more often when the CA is 'pooled up'. Spalted tamarind is usually pretty hard and stable, shouldn't require any special treatment. I actually find that stabilizing using CA in this way can cause more harm than good with processes like drilling - because the CA becomes hard and can cause chip-out when you break across the CA into the material where the CA didn't penetrate. CA can be used for stabilizing while turning, but only turn away thin layers and try not to go past where the CA has penetrated. Just my 2 cents.
 
Thanks. The blanks I have seem rather soft; the last one I tried to work with split as I was trimming the blank. I wanted to avoid problems like that this time, and figured the blank would be dry after sitting around the basement for months ...
 
Dry is a relative term. Just like stale cherrios, wood will soak up moisture from the air. For wood the lowest you get to is something like 3-4% in places like Arizona or up north in the dead of winter. I wouldn't be surprised if your piece was 8% or so - "dry" wood is often a misnomer. For stabilizing, when I say "all the water is removed" I mean ALL, the wood is usually baked in an oven above 212 degF for hours to ensure that all of the water is cooked away then the blank is cooled in a ziplock to prevent moisture from being picked back up.
 
Are you using an end mill? If so, I have found that they are the worst method for trimming soft/brittle materials. I mount in a chuck and square on the lathe with a sharp pointed skew, which gives me a ton of control and I've never had one blow up. Others often recommend sanding (either on a disk sander or a using a squaring jig -- the Rick Herrell squaring jig is often recommended but I've never tried this method or used the jig)
 
Dehn0045 said:
Are you using an end mill? If so, I have found that they are the worst method for trimming soft/brittle materials. I mount in a chuck and square on the lathe with a sharp pointed skew, which gives me a ton of control and I've never had one blow up. Others often recommend sanding (either on a disk sander or a using a squaring jig -- the Rick Herrell squaring jig is often recommended but I've never tried this method or used the jig)
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I keep arguing with myself about whether to spring for a squaring jig or trying to bodge something up for my disc/belt sander. Trying to get the tube itself and not the uneven blank square to the sander seems like the issue. Also, running back & forth between garage (sander) and basement (lathe) just seemed like too much hassle, but I may have to make the leap.
 
I tried several different methods of sanding the ends of the blanks with varying success. I finally broke down and bought the one from Rick Herrell. Glad that I did, it works perfectly.
 
Here is my process: Turn raw blank round, drill on lathe using nova g3 chuck with pin jaws, glue in tube, clean excess glue and then mount between centers turning round again to eliminate any drift from drilling, mount in nova g3 without tail support and using the point of a skew to remove excess material and square the blank.

My skew is ground at about a 30 degree angle, so there is a sharp point on one end. I set the tool rest parallel to the blank and try to keep the tool perfectly perpendicular to the blank. I like to leave a lot of excess for drilling and gluing, this method allows me to remove a lot of material in a short amount of time, but also I figure I can get to within about a thou or two to the end of the brass if I take my time on the last few cuts.

Not saying you shouldn't do a sanding jig, I just find the scroll chuck to be a bit more bang for the buck.
 
Given that I usually have to work in 5min increments when I can sneak down to the shop I try to avoid methods that require changing setups such as changing jaws on the chuck or mounting more different jigs to the lathe, as that chews up any time I have. However, since I just broke another blank trimming I guess I'm going to have to break down and do something different. Maybe some kind of jig to hold tubes square to the disc sander ...
 
I used a disc sander w/o a jig for quite a while with reasonable results, so with a jig setup I'm sure you could get good results and have a dedicated setup. I know I have seen several disc sander jigs posted that use similar concept to Rick's. There are always trade-offs
 
goldendj said:
Preparing some spalted tamarind I bought when first starting, when I didn't understand the difference between spalted tamarind and *stabilized* spalted tamarind. I was worried about it breaking up as I drilled it so I figured I'd soak the ends in thin CA. Imagine my surprise when the it started smoking and bubbling like mad ...

Eventually it settled down, and drilling went successfully, but I was wondering if that was normal.
Click to expand...
What you experienced was an exothermic reaction of the CA ingredients and the paper like structures in the spalted wood. If you ever try applying CA as a finish using cheap papertowels you get the same thing.
 
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