Pour-in inlays?

[Paul Rhoney]

I have a few ideas for doing inlays, branding and such, and I would like to discuss the possibilities and products that can be recommended for this. It's pretty simple, I want to be able mix powdered pearl effect and powdered metal into some kind of clear carrier that will fill a routed cavity. Seems like something that could easily be done with epoxy, but the problems I've had with epoxy are similar to those I've had with other carrier mediums: bubbles. Almost without fail everything I've tried mixing the powders with has not released trapped air effectively enough to cure to a void-free space.

My first priority is finding something to fill a cavity in a headstock veneer, so I can pour or dab (with a cotton swab) in my headstock logo. Yeah I know cutting pearl for a real inlay is not that hard, but I like the look of some of the synthetic stuff, and I'm also trying to find a way to effectively allow me to inlay any color of powder I want. I can make the cavity as deep or as shallow as I want with the CNC machine at the shop, so that's not a problem. I tried routing a deeper cavity and poured in a bunch of white pearl powder mixed with lacquer, CA glue, and Titebond wood glue, and all left bubbles. I thought to make a shallower rout, and fill it in thin layers with the lacquer, which has given me the best results so far, but even with a very shallow rout it still takes a long time to get it filled because I have to thin the lacquer so much to keep it from trapping bubbles.

So is there maybe some brand of liquid plastic made for casting parts that has a better chance of releasing the bubbles from mixing the product than lacquer or glue? Perhaps an additive to a glue that would help thin it to release the air? Do I ave to invest in a vacuum pump, is that the only way to guarantee void-free castings?

[Bill Raymond]

Have you tried applying heat to the infill?

[Paul Rhoney]

No I haven't, but I'm intrigued. So would I just take a heat gun on low to it or something?

[John Sonksen]

I think what you want is a castable polyester resin. There are lots of suppliers for retail and commercial use, I think a big art supply place like Blick's would have it. People use it to encase things for making paperweights. I've used regular epoxy for this before and I know what you mean about the bubbles. I've used a toothpick to coax them to the surface before it starts setting and that works okay. You have to be careful with the depth of what you're trying to fill and the epoxy mix because too much hardener in too deep a pocket can lead to too much heat and cracking.

I do have a friend who's used the casting resin for a table top before and it sets crystal clear, no bubbles. I have not used it myself though so I don't know anything about the difficulty, prep or setup you'll need.

[Greg Robinson]

Hi Paul,

Have you used high quality epoxy like West Systems or System3? They're thinner than the cheap hardware store varieties and self-level and release trapped air bubbles more readily.
As Bill suggested, heat can help. A hair dryer or adjustable heat gun on a low setting, or a lamp can help.
You can also thin epoxy with alcohol (methanol, ethanol, isopropyl, butanol), max 10% alcohol by volume, it gets thin fast!

Hope this helps.

[Paul Rhoney]

Wow, guys, this is great. Thanks so much for the help.

I looked up some casting resins at Blick and found a polyester and a polyurethane. The polyester got quite a few bad reviews, and the polyurethane just doesn't have any reviews.

To answer Greg's question, no I haven't tried West Systems epoxy, all of my epoxy experiments were done using Z-Poxy finishing resin. I am familiar with how easily epoxy can be thinned though, I've done that with denatured alcohol numerous times.

[David King]

You can also buy casting resins locally at Tap Plastics if you have one near you. The mega-source is jgreer.com in LA.
I'd suggest you try a UV cure doming resin (no mixing) so that you don't trap any air in in the first place. http://www.deco-coat.com/uv.html will send out samples.
If you do go with epoxy there's an additive that will supposedly release any trapped bubbles available from http://www.mudhole.com/Shop-Our-Catalog ... y-Mud-Hole
Lastly you can mix the epoxy with a slow turning roller mixer that won't introduce bubbles. http://www.donartrods.com/miva/merchant ... ry_Code=SP
I've tried a vacuum chamber for bubble removal and it didn't help me much at all.

[Rodger Knox]

Have you tried packing the powder in dry and flooding with thin CA?

Cutting the pocket

Overfill the pocket and then scrape it back.

Packed with ebony dust & flooded with CA

And the final result.

[Paul Rhoney]

David, thank you for the links. Do you think there would be any problems with the UV cure stuff when mixed with opaque powders? I just imagine myself pouring this thick black metallic liquid into a cavity, shining the black light on it, smiling at the result, and then realizing that it's still completely gooey underneath the top 1/32", because the light wasn't able to shine past that. Am I making sense? Is that a non-issue?

Regarding thinned epoxy or additives to prevent bubbles I should note that yesterday's experiment consisted of thinning epoxy with denatured alcohol, and so far the results are better than what I've got with anything else. At that point I suppose my only concern would be cost and time. What is going to be the least expensive and least time-consuming method in all of this?

Rodger, to answer your question, yes I'm very familiar with the process of wood dust and wicked-in thin CA glue, I use that technique regularly. In fact the very first attempt at my "pour-in inlay" concept was done that way, and I feel like I can explain why it didn't work. When adding thin CA to wood dust, the dust cannot be too fine. I've found that to get excellent fiber penetration of the dust/glue I cannot sand the wood finer than 220 grit. What had happened when sanding with say 400 grit paper, the dust packs into the cavity, and the glue sits on top. It simply does not soak in enough. With my pearl and metallic powders, I'm dealing with such a fine dust that the glue barely wants to soak in to it, which brings me to the second part of this problem, that the powders are not fibrous and "thirsty" for the glue. With wood fibers, the glue actually soaks inside, whereas the pearl (probably some plastic material) or metallics (obviously some kind of metal dust) do not actually soak the glue inside.

[Randy Roberts]

Paul,
As to the Ca not wicking in, I have a hard time imagining it not doing so unless your bottle has been open for a while and has started to thicken. (You are talking about using the water thin CA aren't you?) I'd try a new bottle before giving up on the CA.

[David King]

Paul,
Good question on the UV opacity. You'll have to experiment with it. I'd probably build up and cure in thin layers. You could also just use it as a filler/ topcoat over the opaque stuff. The beauty of it is that it doesn't need to be mixed and it cures in 5 minutes so you can move right along. Also there is no smell and 0 shrinkage. No shrinkage is a huge asset in this application. It costs more but it saves time, if you like mixing epoxy then stick with that, otherwise Lisa Pavelka is your friend.

Some alkaline wood dusts simply cure the CA before it has a chance to soak in therefore sealing off the surface. Surface tension is also going to get in the way of wetting very fine wood dust. Often you are better off with a gel CA (much longer working time) and hand mixing in the dust on palette before troweling it into the hole.

Oh and if you just want solid colors don't forget about shellac stick.

[Paul Rhoney]

Thanks again David. You touched upon a few points that are important here, that I failed to stress. I like speed, and cost efficiency, but an important aspect of this is being able to fill a cavity in one go with out having to do it in layer after layer. This is why I don't believe the CA glue technique to be the best option for me here. Imagine if you will a skinny 4mm wide channel routed 0.875" deep in a 1.75" thick body blank. I need to be able to fill that whole channel (it's the entire perimeter of the body) in one filling. I need to be able to add my own choice of powdered opaque color to a product that will pour in and not shrink back too much.

I've seen this done before in my own shop, the other guy there pours in a white plastic to do his binding. I want to do the same thing, I just want to be able to do it with a clear product that I can add the powdered pearl/metallic to.

[Mario Proulx]

a skinny 4mm wide channel routed 0.875" deep

Why, oh why, would you route that channel 7/8" deep?!?! 1/16" deep is more than enough, and 1/32" would be just fine... For an inlay.

Sounds like you're trying to make "pour-in bindings", which would be a whole 'nuther deal...

'splain, please.

[David King]

You want a two part polyester, polyurethane or epoxy then. Polyester is going to be the cheapest by quite a bit but it may limit your choices of top coat to polyester as well.

[Paul Rhoney]

Sounds like you're trying to make "pour-in bindings", which would be a whole 'nuther deal...

It is a pour-in binding, I thought I made that clear. I just want to be able to use the same stuff for binding, inlay, and basically any other random wild idea I get.

So I get that I need a two-part polyester or polyurethane resin now, I was just hoping at this point for some recommendations as far as brand and where to get it from was concerned.

[Barry Daniels]

You never used the word "binding" before that last post. How in the world would you pour a binding into place?

[Mark Swanson]

That would be very hard, and a lot of work. If you wanted to make your own binding of a certain type or color then it would be easier to pour it into some kind of a mold and then install it on the guitar afterwards. Still hard to get right, but easier than pouring it on the guitar.

[Paul Rhoney]

I've seen this done before in my own shop, the other guy there pours in a white plastic to do his binding. I want to do the same thing, I just want to be able to do it with a clear product that I can add the powdered pearl/metallic to.

I did say binding before my last post. I described it, then I said what I was describing. Pour-in binding has been done for years by companies like Charvel.

[Mario Proulx]

So, how do you o this? Rout a channel, pour the whatever into it, then rout the body wood off to pose the "binding"? Sounds kinda neat...

[Nick Middleton]

That's exactly it! I saw a video somewhere online showing. It was a factor-tour. Might have been Ernie-Ball?



Edit: Found the video. The Binding process starts @ 2:08 into it.


http://www.youtube.com/watch?feature=pl ... -knWrDYBOc