harden soft wood? making a cherry live edge table

Hi everyone,
I'm making a cherry live edge dining table joining 3 slabs. Some of the wood feels a little soft (when i press it, it is "springy"). I've read that i can use a hardener of some sort but i have no experience. Myy questions are:
1. Should i use a hardener?
2. If so, what type? a very thin layer of clear epoxy? jb-weld liquid hardener? minwax hardener?
3. i'm planning on putting a clear coat on it afterwards. should i finish it first and then put the hardener to get the finish right in case the clear coat doesn't look the same on tiop of the hardener or put the hardener first?

thanks!

The Wood Turners here at SMC have tons of wisdom about this topic. I use thin superglue on sapwood sometimes. I also like many coats of Watco danish oil.

There are lots and lots of wood hardening products available. Most penetrate into the soft wood and then harden, stiffening to "spongy" wood fibers.
As far as a finish, I think that depends on which product you use. I would definitely test on a sacrificial piece before commuting to the tabletop.
Google "wood hardener"

I've used the MinWax wood hardener to repair window frames. It definitely hardens the wood, but it also makes it darker.

Would clear penetrating epoxy sealer ("CPES") do the job? I mean, the stuff is highly caustic and I'm pretty sure it isn't even legal everywhere, but when I've used it in the past, you can make outdoor furniture out of any sort of wood you like...

I have successfully used epoxy based "rot fix" products to harden heavily spalted wood. The products that I've used includes RTG Wood Rot Repair Epoxy and Total Boat Penetrating Epoxy. I think that they are the same product.

Ray - I'm doing virtually the same exact table now with sapwood on the walnut edges. Curious to know what you ended up doing and would you do anything different. Thanks.

My goto for situations like this is Total Boat Penetrating Epoxy, if the wood is reasonably structurally sound, and you just need a hardened surfaced layer - penetrating epoxy is good stuff, but it won't penetrate wood that is merely a bit soft very deeply. I also like it for wood that is so badly blown as to be a sponge - in which case the penetration is great. For the in between cases, where the wood is soft but not really spongy, a thin CA glue will penetrate fairly deeply and firm up softer wood very nicely.

Lots of options for you, depending on how soft the wood is and how you plan to finish it. If you use a ploy finish, you may not even need to add a hardener, depending on how soft the wood is. The same could be true if you used a lacquer finish and built it up. You could also heavily thin out some shellac to get a deeper penetration, or use something like teak oil or a heavily thinned varnish, but it won't provide much strength. But it's a good option if you don't need a ton of strength, just a little beefing up.

But if you go for a purpose-made hardener, I'd test it out on some scrap first to see how it reacts to your stain (if you're using one), how well it penetrates, how well it hardens, and how it effects the finish.

I don't have much experience with hardeners, as I've mostly just used JB Weld for this type of thing (because it's what I have). Thin it out with some acetone to let it penetrate and force it into the wood with some compressed air (I use a vacuum on reverse, as I needed to create a seal around the hose so I'm not just blowing epoxy out, but further in). Then immediately follow up with a thicker layer to fully secure the outside. But that's for rotted wood that's missing parts that's going to be painted or hidden. It's not for stained or natural wood, as it's a nasty dark color. In fact, I just did it yesterday to stiffen up some tines on an old hand plane wedge that was rotting (minus the vacuum part because it wasn't needed). It worked great for that, if you don't mind ruining the look. But it was a user plane, not a collector's, so that didn't bother me. Still, I imagine you could do something similar with a clear epoxy, like Total Boat. Just make sure to use a slow set epoxy if you go this route, to allow time for penetration.

The problem is, epoxy won't penetrate far if there aren't gaps in the wood for it to go into. It's just too thick. Cyanoacrylate glue will do better at soaking into the wood fibers with its capillary action, but it breaks down over time and might cause problems in ten years. A thinned finish, like perhaps 1/2 lb. cut shellac will soak nicely, but won't provide a ton of support if that's what you need. So it's kind of a pick your poison thing, where there are no good options that work in all cases. You just have to access what you're dealing with and go for the one that works best depending on what qualities you need.

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Originally Posted by Jimmy Harris

The problem is, epoxy won't penetrate far if there aren't gaps in the wood for it to go into. It's just too thick.

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There are resin versions that are specifically made to be penetrating and they are very thin in viscosity. They are commonly used for restoration work or for preparing "gnarly" wood for other kinds of processing and/or coating.