Maple 'floater' log turned into epoxy-finished bowl

[Robert Marshall]

Recently, I posted a "tree identification" request here, for a log that floated into my boathouse on Lake Burton (GA) recently. With feedback from replies, and with the additional clues revealed by turning some of the wood, I have decided that it is most likely maple. Watching an ambrosia beetle crawl out of one of the bowls I had turned (but not yet finished at that point) was sort of a clue! The wood shows a bit of ambrosia markings, around the beetle tunnels.

Here's the finished bowl, about 10" diameter by 3" high:

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The photo was taken while the epoxy finish was curing; the bowl was turning on what I call my 'epoxinator,' a 3 RPM spit motor that keeps the epoxy from running or sagging. The bark inclusion visible at the lower edge of the bowl was treated with CA glue to prevent the edge from cracking as it dried (before the epoxy was applied).

My epoxinator has 2 slow-speed spit motors, with PVC pipe spindles and HDPE face plates attached with PVC screw-on fittings on the spindle side, and screws on the wood side. So, I can cure 2 bowls or hollow-forms at a time. Epoxy finishing is a steep learning curve operation, with which I continue to struggle and learn.

Here's another turning from the same log, a plate, not yet dry enough to finish. The grain marking the branching of the trunk at this point is pretty nice.

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Robert

[Paul Williams]

Both are nice, but I really like the grain patterns in the plate. Please post again after you put the finish on.

[John RStegall]

If you get a chance, post some pictures of your epoxinator. The bowl looks interesting.

[Robert Marshall]

Paul asked for photos of the second turning (the plate), after finishing. John asked for photos of my 'Epoxinator.' Both are at my lake house, where I spend most of my time. I'll be back there in a day or two, and will update with those photos. I might also post more extensively on the Epoxinator, which I am using for most of my finishing of bowls and hollow-forms.

[Robert Marshall]

Here's a photo, as Paul requested, of the second item I turned with this wood (a plate). This is a closeup of the grain where the trunk is beginning to branch. The dark line at the left edge, center, is bark inclusion from the early part of the branching. The wood grain above that is running up, from right to left, while the grain below that is running down, from right to left. In other words, the trunk is branching. In between, there is a lot of burly figuring, swirls, little knots, etc.

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And following this are some photos (requested by John) related to the 'Epoxinator,' my name for the dual spindle device I use to keep bowls and hollow forms rotating, slowly, while the epoxy is applied and then cures. It was built into a wine-crate base, using two Creative Cuptisserie Motor Kits from Amazon (this is the stripped-down motor-only version, without all the cup-crafting stuff I had no use for). I started with one motor, then added the second as I came to need to finish two bowls or hollow-forms at a time. The motors run a 2-3 RPM, which is about right. The 'spindles' that I built are PVC pipe, with a screw-on fitting at the end opposite the motor, to which the face plate is screwed. A couple of face plates are visible in the foreground of this photo; I started out using hot-glue, but now mostly use screw attachment through the face plate. One of the face plates shown is HDPE plastic, which I chose because epoxy will not adhere to it.

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One of my supply items is a disposable graduated measuring cup, which will hold up to 8 ounces (which is more than I usually need for any one turning). Very useful for mixing epoxy in the right proportions. Also from Amazon, identified as "SOLO TP10DGM PETE Medical Cup." Box of 1000! You can use them for picnics and parties, too, of course.

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You'll also need something to apply the epoxy to the bowls. I have used the cheapo sponge-brushes (okay, but can shred), the cheapo chip-brushes (okay, but often leave behind bristles which you have to tweezer-off), and silicone barbeque basting brushes. The basting brushes are too expensive to throw-away, but are easily cleaned with denatured alcohol, and don't have the drawbacks of the other choices.

Robert

[David Walser]

Robert -- This is very interesting. Thank you for the information.

[Dave Mount]

IMHO, the way to portion epoxy resin and hardener is by weight. You can buy a cheap digital scale good to 0.1 gram online for well under $10. Then mix in disposable cups. Portioning by weight is much more accurate than volume. You may have to ask the manufacturer/supplier for the correct weight ratio as the density of resin and hardener are not the same. The brand I use is 2:1 by volume but 100:43 by weight. That sounds complicated but there's a calculator on your phone. Hardener = weight of resin * 0.43 (again, for my brand of epoxy, not sure how universal that is)

I can assure you, once you switch to weight for measuring epoxy, you will never go back.

Best,

Dave

[David Walser]

Dave -- In general, I'm sure you're correct. However, some resins are formulated to be measured by volume rather than weight. The instructions for Alumilite Clear Slow urethane casting resin, for example, say to measure by weight, not volume. However, the instructions for Alumilite's Amazing Deep Pour epoxy casting resin say to measure by volume. Perhaps, you might get some benefit by measuring Amazing Deep Pour by weight rather than volume. If so, the company that makes it doesn't believe any such benefit is worth the extra effort. (Perhaps the 'by weight ratio' makes the math hard, leading users to frequently make mixing errors.) At any rate, consumers of Amazing Deep Pour get excellent results when mixing 2:1 (2 parts A to 1 part B) by volume. Why make it any more difficult than that?

[Dave Mount]

Hi David--

The benefit is in ease and accuracy, and I qualified it as being my opinion. I didn't mean to suggest it was "wrong" to do it by volume, I'm just trying to offer an alternative to those that may be interested.

Mixing by weight, if I want to make a teaspoonful today and a one cup batch tomorrow, I don't need to find different containers that have calibrations in the appropriate ranges, I can use any container I have at hand; for small volumes I use cheap generic cups like they serve samples in at the grocery stores (back in the day. . .), or "Dixie" cups or the like for larger amounts. I use epoxy a lot and in a lot of different quantities, from filling small voids or stabilizing unsound wood to building boats. I can see that someone using resins infrequently might not want to spend the $5 to $10 on a scale for these advantages, though I find having a small scale in the shop is handy lots of other uses beyond epoxy.

As to what is written on product labels, I wouldn't infer that dispensing by weight is inappropriate if the directions are written for volume, or vice versa. The instructions on the epoxy I use are for 2:1 by volume, but when I asked the manufacturer for the ratio by weight they had it at the ready and offered it with no caution, knowing full well why I was asking. The densities of liquids like resins and hardeners do not vary appreciably with temperature within the narrow ranges (e.g., 50-80F) we work with them. Moreover, the chemical reactions that take place when we mix hardener and resin are based on chemical masses, not chemical volumes so even if there were density changes, mass would likely be the more stable measure. I cannot imagine a circumstance under which measuring by weight or by volume are not both workable. You can create your own conversion for volume-based directions by simply dispensing an aliquot based on volume and measuring the dispensed mass. I suspect that most directions are written by volume because most anyone can come up with a way to measure volume, but fewer have the means to measure mass.

That's why I said what I said; your mileage may vary.

Dave

[David Walser]

Dave -- I don't think we're disagreeing. I think that measuring is almost always more accurate than measuring by volume. (There may be an exception. If so, I'm unaware of it.) However, there are some resins that are fairly tolerant of small variations in mix ratios. There are also (many) resins that require the mix ratio to be close to standard.

That's why I chose the two resins in my prior post to use as examples. Both resins are made by Alumilite. With one they instruct us to measure by weight and the other we're told to measure by volume. So, the company didn't say to measure by volume out of fear their customers wouldn't have a gram scale. If that was the reason, you'd think the instructions for BOTH resins would be to use volume. Instead, I'm pretty sure the reason they specify mixing by weight for Alumilite Clear Slow is because the resin won't cure properly if the mix ratio is more than just a little off. (I know people who have tried to convert the Clear Slow 1:1 weight ratio into a volume measure by weighing 10 grams of each and measuring the volume. They don't get reliable results. Part of the problem is that the resulting volume ratio is something like 1ml of A to 1.17ml of B. So, using that volume ratio can easily lead to math errors.) Whatever the reason, measuring by volume does not produce reliable results with Alumilite Clear Slow.

On the other hand, measuring by volume produces reliable results with Alumilite's Amazing Deep Pour. Can you convert Deep Pour's 1:2 volume ratio to a weight-based ratio? Of course, but you're unlikely to end up with a ratio that's as easy to apply as 1:2. If I have 1oz of part A, then I need 2oz of part B. Or, if I need 3oz of resin, I know I need 1oz of A and 2oz of B. The math is very simple and can be done in your head. 1:2.435 just isn't as simple to use. Can it be used? Of course! It's arithmetic, not calculus. It's something that all of us can do (with the aid of a calculator). But, we're more likely to make an error. If you're used to measuring by weight, go for it. However, Alumilite spent a good deal of effort to get the volume measure to come out at 1:2, knowing it would produce a reliable result. Simple ratios like 1:1 or 1:2 don't happen by chance. It's the result of effort by the company to make their products easier to use.

Measuring by weight allows you to mix anything from a tablespoon to a gallon of resin. That can be a material advantage. However, there's a downside to measuring by weight that is often overlooked. The resin I use most is measured by weight. But, while I may mix by weight, I pour by volume. That is, if I am pouring into a particular mold, I'm pretty good at estimating how many liquid ounces of resin I'll need. I'm not good at estimating how many grams of resin I'll need to fill that mold. For example, let's say I have a pinecone in a mold made from 3" pvc pipe. I can estimate fairly accurately how many ounces of resin I'll need to fill the mold to cover the pinecone. I'm piss poor at estimating the weight of the resin I'll need to properly fill the mold. It's simply easier for me to estimate I'll need 9 ounces of resin, which means I'll need 3 oz of A and 6 oz of B than it is to weigh a portion of B and guess if that, when mixed with the appropriate weight of A, will cover the top of the pinecone.

So, you're right. This definitely depends on each particular situation -- the type of resin we're using, what we're using it for, and what we're comfortable with. So, definitely a YMMV kind of thing.