Next up - Particulate....
What gets in the way of filling the porespace with resin? – Particulate
This is another quick one, but pretty important. From the earlier posting on the pore system in wood, remember that the typical pore sizes can be categorized into four basic ranges: 10 microns, some that are about 1 micron, some that are about 0.1 micron, and some that are 0.01 micron in diameter. Now … these are pretty small, and any particulate present will lodge in the pore “pinch points” (technically called pore throats) and act as “stoppers” in those pores. They will either completely clog the pores, blocking any resin penetration, or they will effectively make the pore throats smaller, greatly inhibiting the ability of resin to pass that point (next point will be on surface tension, which will make that point clearer).
So – any treatment that intentionally includes significant particulate will pretty much by definition only be a surface treatment of the wood, not a fully penetrating bulk stabilizing process. These are probably fine, as long as you know what you are getting: surface reinforcement only, not a bulk treatment.
As far as acrylic resin-based stabilization goes, you do NOT want particulate present – as penetration of the resin into the wood will be inhibited. There will, of course, be some particulate present … but you want it minimized.
Any particulate present can come from several sources: manufacture, handling, and storage.
As far as differences in manufacturing goes, I just would not worry about the differences between resins. It has been said that the professional stabilizers somehow have higher quality resin – and that they can get resin the home stabilizer can not. By and large, I really doubt that is the case. First of all, anyone synthesizing resin has got to be doing it on a large enough scale to make it economically profitable: a small-scale effort somehow exerting profound quality control would be EXPENSIVE (and it has already been pointed out that the commercial stabilizers are just not that expensive to process your wood through). I have confirmed that K&G does not synthesize their own resin – and I would very much doubt the other commercial stabilizers synthesize their own – it is far too technical and expensive a process. Also, actually it is easier to control the quality of a process with larger or continuous processes. All of the resins I have seen out there are basically in the same price range – which means they are all basically manufactured using the same level of quality control. When you do a search on the web, you are not restricted to seeing those resins just available to the “home” user – you see them all – small scale and commercial scale (sorry, but I have been doing these searches for professional sourcing my entire career…). And … there are just not that many different resins out there. Some are identical, but just re-labeled and re-branded from a larger manufacturer (for example BVV’s “American Made” resin – which is actually re-labeled “Stickfast” resin).
So far I have seen the following resins: Stickfast, Cactus Juice, BVV PC504/66 (relabeled Ultraseal), BVV “American Made” (relabeled Stickfast), Locke / Locktite Resinol 90C, Locktite Resinol 88C, and Paraloid B72 (it is quite possible I missed one or two – please let us know if I did so miss). What is telling, at least to me, is that the direct Chinese synthesizers of the Locke / Locktite resins indicate a production capacity of 4 tons/day, and a minimum order of 200kg. This gives an indication of the scale this stuff is synthesized at. A smaller sized manufacturer simply could not compete. Because they are all pretty much at the same price point – they are probably pretty much equivalent in terms of particulate content. They might have somewhat different formulations (for example Stickfast, BVV “American made”, and BVV PC504 all have viscosities of ~ 2 Centipois, whereas Cactus Juice is more viscous at 4-6 Centipois), and the Resinol 88C has a viscosity range of 5-20 cps … but the basic quality controls (as far as particulate goes) on these large scale synthesis processes are very likely equivalent. Because this stuff is synthesized in such large quantities – I would not be surprised at all if we actually have far, far more re-labeling of imported material than we suspect (thus reducing the actual variation in initial sources). For differences I would simply pay attention to the indicated viscosities – again, I will talk more about that later.
I would be more concerned about particulate introduced or created by handling or storage.
Anytime you handle, transfer, or re-package a material particulate can be introduced. The handling equipment might not be clean, or the transfer can be exposed to the environment (I doubt such transfers are done in an environmentally controlled “clean room” – as these are expensive to build and maintain. Also, the new receiving containers (gallons or thereabouts versus industrial steel barrels the original stuff is put in to) themselves are likely not fastidiously cleaned of particulate (doing so is an expensive and time consuming process). Unfortunately, with the likely few sources of materials, and likely common re-packaging / re-labeling happening, it will probably be difficult to determine up-front which resins have seen reduced handling and re-packaging. Probably the best option we have is, as a community, share experience with specific resins in terms of penetration (but this will be complicated by differences between individuals’ processes). Toss a coin on this one.
Above all, I would be most concerned about storage. For these resins, heat is the enemy in terms of particulate. Technically, these resins need an “activator” to start the polymerization process – but this is mostly a time/temperature thing. Even without “activator” present, there will be some reaction between monomers, especially at elevated temperatures. These reactions will create some level of particulate. Once “activator” is added to the resin, things become more dicey – and much more sensitive to temperature. Technically, even the activated resins will say you can store at room temperature, and that they are “heat activated” – but that does NOT mean that no reaction occurs at room temperature – the reaction is just slower (if you want, look up the “Arrhenius equation” regarding chemical kinetics). Again – any level of reaction begins to create particulate resulting from small monomers creating small “polymers”.
With that background, consider the following: much of this stuff is likely really sourced from China – and it is shipped to the world and to the US in big barrels on slow moving cargo ships. Temperature is completely uncontrolled. Even for un- “activated” material, there will be some level of particulate generation, especially when the ship hits tropical waters, and thus uncertainty in terms of particulate level. If you buy domestically a gallon of “activated” resin (whatever the brand), that gallon container is trucked around in non-temperature controlled truck trailers, which is the sun on the open roads will get HOT inside. More uncertainty. When you store that gallon container at home, you have more control, but again, even at room temperature, there is some level of reaction going on.
So, how to deal with all this? I would recommend the following: I would look first to domestically manufactured resin (it sees less exposure to temperature extremes when sitting on a ship for months). Second, use only non-activated resin, and add the activator yourself when at home (“non-activated” resin sitting in a hot truck on the highway will be much less sensitive to polymerization reactions than “activated” resin sitting in that same hot truck. Third, when you get your resin at home, whatever the source, store it in the refrigerator. All chemical reactions speed up at higher temperatures, and slow down markedly at lower temperatures. The difference in reaction rates between room temperature and refrigerated temperature depends on the specific system (and we do not currently have enough information on this one), but it can only help. (aside, it is quite possible that “freezer” conditions might be ok and thus even better … but we do not know enough about the resin to determine that. Has anyone out there tried storing your resin in the freezer – and what was the result?)
This turned out to be longer, and more “stream of consciousness” than I thought it would be – but hopefully it makes sense.
I think in the next posting I will try to tackle “surface tension”. This is probably our biggest issue to full resin penetration (but wont know until I crunch some numbers) … and also the most misleading and difficult to understand (it definitely requires pictures ). But once understood, it is really cool, and will help explain a lot about the application of pressure during the impregnation process…..