I have now processed the results of my sets of experiments and even found time between grinding to conduct a new one. To recap though, I wanted to see if there was anything you could soak a loose axe handle in to swell it sufficiently to fix it. I tested Veritas chair doctor glue, Water, PEG, Boiled linseed Oil and thinned BLO
I will start off with the Veritas Glue- This worked to a degree but running any glue that is thin enough to penetrate between the handle and axe would also work. I could find no evidence of the wood actually swelling, but then I was not using the glue as intended. You can see from the picture that the glue did not penetrate very far and rusted the socket. Gluing is not a method I can see myself using as I like to be able to disassemble my axes so leave a protruding wooden wedge.
Water-An average of 4.1g soaked into the wood. This swelled the wood massively, but in drying the wood had been crushed by the swelling and were so loose that they could be rocked in the socket. You can see the constriction here. So not a long term solution but in an emergency it will temporally secure a loose head. It was interesting to measure the differential expansion coefficient- this came out at 2, the Ash moves twice as much tangentially as radially.
PEG- This didn’t work as hoped. The wood swelled, but as it dried it shrunk back, it was slightly looser than before. Ideally PEG should be applied to wood that is green and if using dry wood it is recommended the wood is soaked for a few days to rehydrate it, this allows the PEG to penetrate the wood better, it was very viscous and the amount absorbed by the wood was less than for the thinned Linseed oil at 1.8g. I don’t see that soaking a loose head in water for three days and then soaking it in PEG a realistic idea. I wouldn’t like to leave my axes submerged and rusting for the best part of a week.
BLO- The immediate swelling I expected to see did not occur, however as the oil cured it should gain weight by oxidation- in theory a weight gain of 40% is possible in raw linseed oil, somewhat less in BLO due to the added driers. A gain in weight suggests an increasing in volume that I thought may give rise to the swelling that I was hoping for, so I have been recording weights for the last few weeks. This was not found, despite using scales that weighed to one hundredth of a gram, no consistent weight gains were recorded. Changes due to humidity were recorded in all samples and it was found that these changes were less in the BLO samples- the oil reducing the flow of water vapour from the air to the wood.
Thinned BLO- Broadly the results were the same as BLO, I found it interesting though that significantly more oil was absorbed even taking into account that some of the initial recorded increase in weight was just the white spirit used to thin the oil 2.1g of thinned oil went in equating to 1.7g of BLO as opposed to 1.2g of BLO if it is not thinned ( It should be pointed out that it is likely that the BLO I was using had some thinners in to start off with, but I was amazed at how much thinner the oil was with 20% whites spirit, I would guess that there was 5% or less thinners in the ‘neat’ BLO). This seemed to evaporate off quite quickly. It does seem to be worth thinning BLO not only will it penetrate deeper but more goes in as well. However in splitting the samples open at the end of the tests it was apparent that not all the white spirit had evaporated off- it could be smelt easily. It can be seen how the Thinned BLO penetrated the ring porous sections of the Ash.
So not the set of results I was hoping for, but I remembered reading that wood treated with BLO resisted compression better as the fibres were filled and less likely to collapse. Perhaps this means that if the wood gets wet and swells it will resist being crushed and then shrinking on drying as seen in the water samples? Also the Axe will transmit force to the eye- these concussive blows may dent the wood allowing the head to come loose. However in the axes I have used it tends to be periods of storage that cause heads to loosen rather than use, but then I forge my heads with a larger contact area than many reducing the pressures on the wood.
I didn’t have time to run a series of tests to see how the samples fared against compression over time, but I did set up a test imitating the concussive forces that an axe or hammer might impart to a handle.
Not the clearest picture I am afraid but we used a bar of steel that was held a set distance above the samples ( by the box section that also guided it down onto the target peg) We dropped this three times onto the samples radially and tangentially then measured the degree of crushing. We tested BLO samples against some control samples I had kept for such eventualities.
In these samples we found that they were crushed much more radially- the growth rings more readily crushed into one another, not really a surprise if you have every tried pounding ash splints. Tangentially however the depth of crushing was roughly half.
In BLO loaded samples this effect was not seen, the tangential crushing was reduced slightly, meaning it was slightly stronger. However the real surprise was the radial strength this was now equivalent to the tangential strength.It seems that the BLO filled the pores of the ring porous ash and reinforced it at this weak spot. No statistical difference was seen between the thinned and uncut BLO despite the thinned seeming to have penetrated more readily.
So what did I learn? Well..
Soaking in water is as bad as thought.
PEG and Chair Doctor glue don’t work.
Boiled linseed Oil didn’t work as expected- there is no point soaking a loose head and expecting it to swell and tighten up; however the wood does seem to be slightly more resistant to moisture after oiling so will move less after treating. Ash will also see an increase in compressive strength after treatment that may help it to stay tight in a head. Thinning BLO allows more to go in, reducing the soaking time needed. Probably better to use it neat for a final coat though. BLO is not the cure all that I hoped it to be, but out of all the samples tested is was the best.
As many of you will know Don now does the IT support on my site, and is very knowledgable on the subject of Linseed oil, we have been communicating over the last month or so, it was he who confirmed the idea the the oil should gain weight as it cures. I initially found great comfort in this, I had made an axe stand from some oak years ago and as some of the sapwood had rotted, so I poured litres of BLO into it, the idea being that it would soak into the punky wood, cure and harden it. It didn’t work like that, 15 years later bits still flake off and leave oily smears as it still hasn’t fully cured. I had increasingly found that this stump wasn’t so easy to lug about and had been putting it down to encroaching old age, so the idea that the stump was still getting heavier as the oil cured was encouraging. With these results though I am afraid I have had to revert to the previous theory.