For those who haven't tried it yet, resin inlays are pretty straightforward in concept. You CNC your design into wood (or the material of your choice), pour in some resin of the appropriate color (I'm using dyed Alumilite Clear Slow, but epoxy, while usually more viscous, can often be made to work too), then do a facing pass to clean off the mess after it cures. Simple, right? For those who have tried it, I could use some advice, because it's not quite so simple in practice. The problem I'm having is that if I throw the job in a pressure pot to crush the life out of all the miserable little bubbles in the resin, the color bleeds into the grain of the wood... and, conversely, if I don't use the pressure pot, I get bubbles, resulting in small (and not-so-small) voids in the finished design - especially in the finer details. In the test piece below, I've somehow managed to get bleeding and some small bubbles - because I'm talented like that. I've tried sealing the design & surrounding wood with wipe-on poly and with shellac, and neither one seems to have helped (it may have actually made the bubbling worse, even under pressure, but I didn't test far enough to be sure of that part - just that it didn't stop the bleeding). I thought about stabilizing the wood first, but at 8"x12", the piece is way too big for my vacuum chamber (and I don't have a clear lid large enough for the pressure pot to monitor the process), so that's out, too. I believe the usual method of treating voids in resin is to drill out the bubbles & re-pour, but with all the fine lines, that's not so practical either. Anyone else have any experience with this? Anyone else have absolutely no experience but a brilliant guess? Anyone? Please? -Bats (Hell, at this point I'll even settle for kinda-stupid-but-well-intentioned guesses)
When you're casting in a silicone mold and something like this happens, you do a print coat- a very thin, brushed-on layer of your resin (or sometimes a similar one with more appropriate properties). So instead of doing the pour first, brush in a thin layer of the same resin and let it set, I dunno, 70% (so it's setting up and won't bubble/run/push into pores, but still tacky enough to bond positively to the full pour). Then do your main pour and pressurize- it shouldn't be able to penetrate the almost-cured resin, but that resin should also be thin and deep enough to not have visible bubbles.
I thought about trying that... but if you take a look at the design, a lot of those lines are maybe .025" wide by not much deeper, and I think the Alumilite, while thinner than most epoxy, is probably too viscous to allow two layers in there - plus the problem of leaving enough color at the bottom to survive the cleanup facing pass. That said, I'm short on other options right now, so I may try to give it a shot tonight. Any brush recommendations? If that doesn't work, any suggestions on a very low-viscosity clear resin that doesn't charge $25 for shipping? (I had to skip the Smooth-On Onyx you suggested on the Firefly project for that reason, Rob... Blick carries some of their varieties locally, but not the Onyx). -Bats (insert dumb comment here)
Do Alumilite make a thinner for their resins? Smooth-On make both a thinner and thickener for a lot of their products. It's weaker with a thinner, but it might be the only way to make it work, and it's not holding much as an inlay. I'd assume a fine bristle oil-type brush, like a nylon/polyester blend, or something like that would probably be good. Anything that's gonna minimise texturing and get in the finest crevices without overloading the brush. And yeah, Smooth-On do charge a bit for shipping, I don't usually order from there until I have comfortably over $200 of material to order (not that that's exactly difficult when buying Mold-Star silicone by the gallon...). Thought maybe it'd be less if you were only buying a trial kit, but ah well. Worth picking up the Onyx at some point in future when you get a chance, though, it's good stuff.
Try a heat gun.. it's what they generally use for large pours to get the air out. Yes, you can thin epoxy, well not thin, but extend it's dry time to allow it to level better. You really do need to try to figure out a way to brush on a thin layer, because wood is porous, and air will be drawn out of the wood into the resin during the curing process. The other option, since your image is so shallow, is to spray on a sanding sealer, or a few coats. This will soak into the wood, closing off the pours, and will also prevent bleeding. Then run your cnc carve, and do the inlay etc.
Sadly, no. : "There is not a chemical available for purchase to make Alumilite Resin a thinner viscosity. We do have thinner viscosity resins than the Regular Alumilite at 190 cps. Our RC3 (110 cps) and Alumilite White (90 cps, our thinnest resin) are thinner than the Regular Alumilite"...and both the RC3 & white are opaque (I can't find any mention on their products page of a "regular" Alumilite). The Clear Slow is 400cps. So probably not the acid brushes that I seem to have ended up with so many of. Figures. The next challenge will be getting the whole design (the pic was just a corner of it) brushed on within the 12min pot life. It makes me really miss my 30min epoxy. And I'm assuming (hoping) that figure you gave is ~70% of cure time, not ~70% of pot life? It sounds nice, but, yeah, it's hard to justify paying nearly as much for shipping as for the resin, and I don't really go through the stuff in vast quantities (for me, mixing up 10g at a time is a "big batch"). I may have to give Blick a call at some point, though. They don't carry the Onyx, but they've got a lot of the other product lines, so there's a chance I can convince them to order it for me. In any case, while it might've gone better with the Onyx, that particular project still came out well enough: In the end the only problems were some pinholes (especially in the small "O"s), and a few scratches that just didn't want to sand, polish, or buff away. I don't think I even broke a cutter on it (which is good, since I didn't have a backup tapered endmill) It probably wouldn't stand up to the elements stuck on the outside of a car (and I don't know whether thermal cycling will cause the resin to pop out over time in a car), but I'm reasonably happy with it. -Bats (shiny!)
I've tried a heat gun in the past (well, on epoxy, not Alumilite), but always ran into trouble finding the sweet spot. If I got rid of the bubbles while the resin was still open, half the time I'd find that I'd cooked it, and would get foaming below the surface when it finally set. I think the preferred route is lightly torching the surface, but I'm working in kinda cramped & flammable quarters, so I've been a little reluctant to go that route. Except I'm not using epoxy (Alumilite Clear is a urethane resin), and cure time/leveling isn't really the problem. Actually thinning it would've allowed for coating the inside of the small details without filling them in, but according to the mfg, that doesn't seem to be an option. Trying that will be the next step. *crossing fingers, legs, and eyes* I haven't played with spray sealers, but most sanding sealers I've tried are little more than highly-thinned poly (or moderately-thinned wipe-on poly). I tried both poly and shellac (after carving, brushed into & around the design), and neither seemed to make a difference : On this test (this time on MDF - cherry's a bit pricey to keep throwing away on experiments, and while the two penetrate differently, the effectiveness of a sealant should be the same on either one) the top half was coated in shellac, the bottom half in wipe-on poly (both in and around the design), without much visible difference between the two. -Bats (and here I thought 'bubbly' was supposed to be something enjoyable)
One other thing that hadn't occurred to me before... I've still got a couple cans of CPES ("Clear Penetrating Epoxy Sealer" - read: a whole cornucopia of solvents with a dash of resin) left in the garage from another project, which sounds like the sort of thing that should work. Of course, the drawback is the two day cure time, which makes testing a mite tedious. -Bats (which may or may not be better than tedious mites)
Howzabout sealing the wood with epoxy first before cutting? I have built a fleet of cedar strip canoes and kayaks (and one pirogue) and I always sealed the wood first before putting the fiberglass on. No bubbles. If the wood you are using is really porous, the epoxy will get way down inside and harden. Then when you engrave, you remove the wood and some of the hardened epoxy but everything around the engraving should be sealed.
Yeah I just looked and it doesn't look like Smooth-On have a urethane thinner either, so maybe it's hard to do for that chemistry. They do have an optically clear epoxy with a 5-hour pot life (EpoxAcast 690) and clear epoxy thinner (Epic Epoxy Thinner) though, which could be worth looking into if you didn't have, like, a week to get this stuff finished up. Right. Tacky- but probably slightly past the point of leaving fingerprints in it, I would hazard to guess. Would need to test, I'm sure. If they use Smooth-On directly as a vendor, they should be able to order it in, I would assume. Wouldn't have to worry about it sitting on a shelf for any period of time, either- the other reason I prefer to order from Smooth-On direct. Yeah, looks pretty good. Can't complain at that result. I've wondered about that before too. I'm not sure, off-hand. This table - Coefficients of Linear Thermal Expansion - has steel around 12, alu around 24, and resins around 55. Which probably isn't a a problem through the thickness of the material, but it could make larger badges like this tricky widthways. It's only in microns per meter per degree though, so that's not a whole lot of expansion. It's also odd, because I thought epoxy was more stable than that, but maybe that's only when it's filled. Smooth-On make pre-metal-filled and pre-mineral-filled EpoxAcasts for industrial tool and die work which should be pretty thermally stable but don't include TCoE data in the technical bulletin, for some reason. Of course they also make flex and semi-flex urethanes which could probably work as well if they don't get too damaged by cold or UV.
Now that's something that (despite @ljvb's suggestion of pre-treating with sanding sealer) I hadn't even considered. I don't usually think of cherry as being especially porous, but obviously it's enough so to allow for the bleeding, so presumably it would also be porous enough to allow for the sealing coat to penetrate - especially if I put that under pressure too. Thanks for the idea. I may see if I can fit that & Rob/Peter's suggestion in today, if the pressure pot cycle time & another project don't eat the day too quickly. -Bats (ready for the damned elf season to be over. I want to make my own toys now!)
As a potentially faster option that I just thought of, set it on the machine (in a G55 position if the initial cure time's long), machine the design, brush in any old short cure time clear resin (5 minute epoxy?) that'll soak into the surface, re-machine the design to take out any excess cured resin, then take it off, tinted-resin-fill and pressure-pot. I don't know how well one would stick to the other (though urethane has a habit of sticking to absolutely everything), but maybe a handful of tiny drilled holes straight down into the wood in places where the resin can't come to the surface in an obvious way would help hold it in if necessary. Of course this is heavily dependent on the repeatability of the machine, but if it isn't turned off and doesn't skip steps, it should be fairly ok.
Update: Most of the day got sucked down into a big constructiony project, so I just managed to start the tests. I'm going to be stuck waiting a few hours for the resin to cure in the pressure pot, but I suspect Peter/Rob (Peterob?)'s brush coat idea is a wash - at least with this stuff. It took me pretty much the entire pot life just to cover the test patch (less than a quarter of the finished piece), and the fine lines would fill up almost immediately. I ended up tossing it in the pressure pot (rather than waiting for a partial cure) in hopes that it would force some of that resin into the substrate, rather than just clogging up the design. I'm still holding out hope for Giarc's suggestion (also currently sitting in the pot). It certainly looked like the resin was being absorbed by the MDF. Cherry's a fair bit less porous, but if it seals the MDF, I'll take that as a good indicator that it's worth testing on the real wood. -Bats (pour. porous. poor us. pour us a drink?)
So... I tried both of the current contenders on MDF - Peter & Rob's suggestion of a brushed on coat (center), and Giarc's idea of pre-sealing (right), both subjected to 70psi for a full cure plus a few hours (I've been busy in the garage, where the pressure pot isn't). I don't have a post-pour pre-pressure shot, but the fine lines were, as I mentioned earlier, partially/entirely filled with resin. That, as you can see, cleared up nicely after being pressurized (although the amount of time I had to spend on the brushing would still be problematic): After the final pour, the results were... unfortunate: I can see a bit of a clean halo around some of the brushed-on bits, but only after I've gouged away most of the design. The pre-sealed test looks an awful lot like the earlier un-sealed versions. Anyone want to hazard a guess as to how the color (and presumably the resin that carries it) is sneaking through a cured layer? I'm half-tempted to try both on the cherry anyhow, for lack of any good alternatives... but I hate wasting good wood like that - especially without any indication that things are likely to turn out any different. Although... any guess as to whether maple might be less porous than the cherry, and less likely to bleed? -Bats (anyone want to hazard a guess as to how much hope I'm still holding out for this technique?) (anyone want to hazard a guess as to my patience?)
Is this my original print coat plan or my modification of Giarc's pre-seal plan? I definitely think the latter has merit.
I've thought about trying to spray something on it (I've seen recommendations elsewhere to use a spray coat of lacquer or shellac), but I think the only thing the resin will do to my spray guns is choke 'em. That was your original plan & Giarc's original plan. I haven't tried your modification yet, because A) I'm lazy and working across the keyboard & side of the machine to apply the seal coat is going to be a pain in the... bats, and B) I'm skeptical of the ability of the 5min epoxy to actually soak into the surface deeply enough to make a difference - or even fill the narrower channels of the design, since the stuff I've got is listed as 10-12k cps, compared to 400 on the Alumilite. A question, though: Do you think that would make a difference, when neither the brushed-in coat nor the surface coat (which your idea seems to combine) did? -Bats
A bit of a long shot, but is there any chance a post-carve coat of spray paint would both stay on the surface and seal against bleeding? (also, just picked up some maple for testing, on the off chance that it bleeds less) -Bats (bloody cherry. bloody maple. bloody mary? only for breakfast.)
With the right thinner it should work... Catalyzed 2K is urethane, after all. Just gotta clean out the gun fast and thoroughly. And watch for line moisture. And air moisture. Yes. It needs to only fill the wood a few cells deep, because you're machining to the surface it actually needs to seal, not just sealing the entire block and hoping it soaks in deep enough. Pre-machined, it only needs to fill a few cells deep into the wood- which even 5-minute epoxy should be able to do, but I think you can thin it with xylene or something if necessary. After it's re-machined, you're basically pouring your tinted resin into a plastic dish.
Which isn't available, at least in any official capacity. Very fast. And that. But given the lack of a thinner, the fact that I'm at least a step or two below "barely competent" when it comes to spray guns, and the fact that it's below freezing out, I've got a sneaking suspicion that any spraying-based (or at least non-can spraying-based) solutions will probably end up pushed to some other project. I guess what I'm trying to understand is how the end result is any different from the post-machining brushed-on print coat method, which would (theoretically, if not practically) also turn the carved design into the same sort of plastic dish. I'm also a little leery of the xylene - primarily on the grounds that any industrial chemical starting with "X" or "Z" is automatically scary, but also because I'm running out of space on my solvents shelf & don't really want to add yet another can of something toxic, explosive, and unlikely to be used up any time soon. Any thoughts on other thinners? Maybe alcohol (which I've occasionally used when degassing as a surfactant and/or to pass the time while waiting)? West System says a fair bit about problems with solvent-thinning (almost all of which are irrelevant in this case, which is good), but little about the differences between solvents. Is there some particular advantage to xylene? -Bats (trying to understand many things. among them, why the language doesn't include enough profanity)
Yeah it'd be some kind of automotive repair place, if anywhere. Most places order urethane paints in, I think. Catalyzed urethane paints are extremely persnickety when it comes to atmospheric conditions whilst also being, I believe, quite toxic. They're really not very usable without a booth, in practice. In theory, they're very similar, but only if the print coat is applied fairly perfectly uniformly and soaks in consistently, you don't want to over- or under-apply it. But when you're machining the resin back out, whether it fills in all the details or not is irrelevant, if you lay it on too thick or it's too runny or not runny enough doesn't matter nearly so much, you're getting the consistency you need from the machine itself. It's a process thing more than a result thing. Not off the top of my head, unfortunately. I've just seen it bandied about the most when people are talking about thinning epoxies. Obviously speed is key here, so you really don't want to thin it very much at all anyway, if it's avoidable. Any other high-speed resin will also do fine. Onyx FAST might work here, at 150-second pot life... Wonder if there are any other suggestions on that can of penetrating epoxy's ingredients?
That's sort of the impression I'd gotten. Especially the "toxic" part. Ok, I guess I can see the advantage there.. but Is speed anything more than a convenience here, or is there some other advantage beyond freeing up the CNC? Either way, I don't think I'd want to use CPES, with its 2-day cure time. How about Onyx HOLY **** NOT QUITE THAT FAST? Although, even if it were available, I have to assume Onyx would have the same bleeding problem as the dyed Alumilite, wouldn't it? Sure! We've got Isopropyl Alcohol, Butanone, isobutyl isobutyrate, Methyl Propyl Ketone, Methyl Isobutyl Ketone, Propylene glycol monomethyl ether acetate, Di-isobutyl ketone, Toluene, Cyclohexanone, Methyl Isoamyl Ketone, iso-Butyl Acetate, Methyl Amyl Ketone, Diacetone Alcohol, Ethyl Acetate, 3-éthoxypropionate d’éthyle, Xylene, Methylamyl acetate, (2-methoxymethylethoxy)propanol,Solvent naphtha (petroleum) light aromatic, all listed as <50% by weight. And probably a dash of epoxy. I seem to remember reading that MSDS ingredients, rather like food ingredients, are listed from most to least prevalent - which would suggest alcohol's the biggie - but I don't know whether that's actually a requirement. Also: Today I've got two test to surface - dyed black resin on maple, and an attempt at pigmented white resin on cherry... although zinc oxide - while essential for fire extinguishers, your artificial limb, telephones, car batteries, and handguns - doesn't seem to mix smoothly enough for coloring resin. -Bats (come back, zinc!)
Trying to think here, and I don't think so? It's really just to get it off the machine as quick as possible. I would imagine the shorter the cure time the less penetrating it's going to be in directions you don't really want it to be- though that's more a function of its cure profile, really. If it gels quickly but solidifies slowly, that's just as good. Yeah I don't even know who uses it with 2.5min pot life. Though 15 minutes to demold is quite something, if you're up against a deadline wall. I would imagine that very fast resins would bleed very little- they literally wouldn't have time to significantly percolate through the cells before gelling. Lotta ketones in there. Got any MEK? Not sure what the alcohol's for, but if epoxy dissolves in it, I don't see what the problem would be. Could you sift it in like a pretentious baker?
Of course, it also means it'll be less penetrating in the directions I do want it to be. The demold time would be great, but I don't think I could even mix it & bring the pot up to pressure in 2.5mins, never mind doing anything useful with it. I'm also used to the slower resins being a bit more viscous - although that may just reflect on the brands I've used. Nope. Lots of alcohol, acetone & mineral spirits, but I'm short on the more exotic solvents (or, well, the more exotic of the hardware store solvents), and unfortunately they don't seem to stock tiny enough cans for my purposes. I tend to use alcohol for cleaning uncured epoxy out my glue trays, so it definitely thins/dissolves it. I just don't know what other side effects it might have. That actually might do it, if I had a small, disposable sifter (this would probably be my last reply if I got caught stealing one from the kitchen), since clumping does seem to be the main problem. Here's what it came out looking like: You can see the worst of it at the bottom of the pre-surfaced pic and in the fine lines at the top of the post-surfaced, but there are a scattered chunks in other places, too. I've actually had several batches of the un-tinted supposedly-clear resin turn out a beautiful opaque white, but I have no idea how to deliberately replicate it. -Bats (in search of a heater. for me, not the resin)
Amine blush perhaps. West Systems is great at forming amine blush on the surface which normally is a bad thing. It can prevent layer adhesion and has to be removed by hand scrubbing (so much fun). I used their over-priced crap on one project and moved on to another brand and experienced great joy due to the absence of amine blush.
I've still never seen amine blush, although I did use West Systems for a large coating project a couple months back (I've still got some left, and was thinking about trying to use it for this project, but the viscosity is higher than the Alumilite, so I didn't see much advantage. Plus amine blush). I had the impression that's a surface effect on epoxies, though, and this was straight through a quarter-inch thick urethane casting. Does that still sound likely? -Bats (*blushing*)
No, that probably was not the cause. Amine blush is a surface problem that really is only a problem if you are building a boat and have a busy life which does not always allow you to add more coats of resin before the first coat has fully cured. It can be scrubbed off (not fun). Well, there may be other case where it is a problem, but the aforementioned was my problem. Switching brands for future builds solved it.
I was working on a 18ft replacement panel for a garage door, and was really dreading the idea of scrubbing it (or of dragging it somewhere it could be scrubbed). I got lucky on that one. Boats are a bit beyond me, though. They've always struck me as fantastically exciting projects (I recently visited a guy who does a lot of Chris-Craft repair/restoration work & got to drool over the boats)... but space constraints mean most of my projects can be measured in inches. Even if I could find the space to build a boat, I don't know where I could put it. Or how I could get it down the hill & through the woods to grandmoth to the river. -Bats (maybe I could make a bathtub yacht?)
