Liquid Glass Wood Finish

For several years now I’ve been making woodturnings, carved bowls, trays and plates. Making items like these that will potentially see real use as tableware; subjected to food, water, oil, soap, etc, has put me on a search for quality finish options that are not only food safe but capable of handling heavy use and cleaning. The go to options are usually oils or oil/wax mixes of some kind, and while they can certainly work, they also have their downsides. Here in Japan urushi lacquer has a long history of use on tableware. Urushi is incredibly durable, but using urushi also presents some really serious challenges. Recently I’ve been using a new finish, often called “liquid glass” (液体ガラス) here in Japan, and so far the results have been really promising and exciting. So I thought I’d share what I can about this finish. But first a quick look at the alternatives.

Urushi

One finish that I’ve been interested in for many years is urushi lacquer. Urushi is a natural finish sourced from the sap of urushi trees here in Japan (and elsewhere in Asia) and has a really long history of use. It’s also really quite durable against water, heat and even acid, alkali, and alcohol. Drying takes time, but that also means that there is little rush when applying the finish, and a variety of cool techniques can be used exploiting it’s long open time. Two techniques which I’ve been interested in for a while are the crackled egg shell finishes (ran-gaku-maki-e 卵殻蒔絵) and sabi-urushi (錆漆). These techniques are good examples of the kind of range you can achieve with urushi. The egg shell technique involves carefully cracking and embedding piece of quail eggshell into the lacquer to create really detailed and intricate patterns. Sabi-urushi is made by mixing urushi with very fine powdered earth, creating a texture that can be reminiscent of pottery. The egg shell technique is incredibly refined while sabi-urushi has a much more rustic feel.

The surface treatment possibilities that urushi offers are truly immense and the craft and techniques run deep.

But as many of you may already know, the BIG downside to urushi is for those of us who suffer from allergies to urushiol resin that is naturally present in the uncured lacquer. Urushiol is the same resin found in poison ivy, poison sumac, and poison oak. I happen to be highly allergic, and despite taking serious precautions such as long sleeves, nitrile gloves (sometimes using a long pair of kitchen gloves on top of those!), and working out of a container where I stored and applied the finish in an attempt to contain both the raw ingredients and the workspace itself, I still ended up with major whole body rashes.

So I’ve thrown in the towel when it comes to working with urushi, which has led me back to a quest for a quality and durable finish for tablewares.

Oils/Oil and Wax Mixes

The classic and simplest options for wooden tablewares are oils and oil and wax mixes. I used to use a mix of beeswax and mineral oil which was super simple and easy to apply. More recently I’ve been using raw linseed oil and beeswax. Oils and oil/wax mixes require periodic maintenance, and some folks are not so keen on that. Linseed and tung oil also have a bit of a smell which can be a turn off for some people. Oil finishes only add a modest level of protection, and require a bit of TLC to maintain the finish if you want to preserve the woods surface.

So oils, being easy to apply and relatively safe compared to urushi are okay, but they are also kind of lacking when it comes to durability and they require periodic maintenance.

Liquid Glass Finish

Meanwhile, over the past few years I’ve repeatedly seen other furniture makers here in Japan using a finish called “liquid glass.” My wife and I met one guy using a liquid glass finish on sugi (Japanese cedar) plates that he was making. He told us that the surface left by the finish was really durable and strong, producing a coating that would give an urushi-like level of protection. And on top of that, the finish is nearly unnoticeable. Handling those sugi plates I was incredulous, thinking the guy was just selling us some hype. The plates looked and felt like they had no finish at all, yet he was telling us that they were extremely well protected.

Fast forward to a few months later and I caught wind of the liquid glass finish again, but this time through a fellow woodworker in the states. That encounter eventually led me to Jarrod Dahl’s website where he has a blog post about this finish, and has even imported and been selling it in small quantities in the US. Jarrod’s site was the first time I ever found any real information on liquid glass in English. Reading his description of the finish and it’s potential really piqued my interest.

Turns out the guy with the sugi plates wasn’t making stuff up. This finish really is supposed to be extremely durable and tough, and has also been thoroughly tested to meet safety standards as a food safe finish here in Japan. The super simplified description of this finish is that silicon molecules in an alcohol solvent soak into the wood, the alcohol evaporates, and over the course of a few weeks the silicon bonds to the wood’s fibers, forming a glass-like coating. I’m no chemist and really don’t understand the science, but I’m sure there must be more going on chemically to cause the silicon to bond to the wood and form a hard coating. But from the research I’ve done thus far, that seems to be the gist of it. (I’d love to see a Bob Flexner level article on this finish.)

I eventually bought a jug of this liquid glass from the Japanese manufacturer Tatara, and have been using it on plates and bowls for the past few months. I coated a couple of pieces to use and live with as well, and I’m doing my best to use these pieces like I would normal ceramic tableware, meaning washing them with regular dish detergent and a sponge, and towel drying them after each use. So far the results seem really promising.

It seems that “liquid glass” finishes for wood have been in use in Japan for the past 15 years or so. And initially I think they were developed for use on wooden buildings to protect wood from rot, staining, and to even increases its fire resistance. (Check out this youtube video to see some fire resistance demonstrations). So compared to urushi and oils, liquid glass finishes are still relatively new, and time will tell how they fair long term. Nonetheless this type of finish seems like it has a ton of potential.

Actual Use/Performance

As for applying the finish, it’s super easy. You just brush it on fully saturating the wood, wait 15 min and brush on a second coat again saturating the wood as much as possible. I’ve found softwoods really soak up the finish, far more than hardwoods. The next day a third coat can be applied if desired, but I found 2 coats that really saturate the wood seem like enough. Since the alcohol/silicon soak into the wood there is no surface film to be damaged, so you can safely handle pieces soon after the solution fully soaks in without risk of messing up the surface. After 3 weeks the finish should be fully hardened and ready for use.

I’ve been testing out a few pieces here at home, including a small cherry bowl that I’ve been using and washing on a daily basis now for the past month and a half. Putting water in the bowl the first time was interesting. The water really beads up on the surface, with no indication of soaking into the grain whatsoever. That effect diminished as I’ve used and washed the bowl. Now water does more noticeably penetrate the surface of the wood, but even so, after continuing to use the bowl on a daily basis, washing with soap and water, and drying, there seems to be no real change to the woods color, no grain raising, and no splits or cracks from repeated soaking/drying. So far so good. Other pieces that I’ve been testing, have maintained that initial hydrophobic surface where water just beads up and flows off, so it may be that my cherry bowl was just not coated heavily enough. I also may have rushed things and didn’t wait the full 3 weeks for curing…. I was too anxious to try things out!

I think this is also a great finish for softwoods, which can be particularly challenging to finish. As someone who uses hand planes, and other cutting tools, the finish left by a sharp blade on softwood is particularly glossy and pleasing. But oiling or applying other finishes to a softwood often end up completely changing the finished look. Liquid glass is the first finish I’ve ever used that looks really good on softwood, because it has a minimal effect on the finished surface, and leaves a very natural look to the grain without changing the sheen of the wood left by a tool.

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To quickly recap, here are some of the pros/cons of this finish.

Pros	Cons
Super easy to use and apply	Expensive – 1 L was around $150
Minimal to no maintanence required	Availability incredibly limited outside Japan
Minimal change to the woods/color sheen, great on handplaned and carved surfaces	No surface treatment options available like urushi, and no sheen variations (gloss, satin, etc.), the surface left on the wood by tools or sandpaper is what you get
Once cured safe for use on tablewares	Still a relatively new finish and not time-tested like urushi
In use, seems to provide a really high level of moisture resistance compared to oil and oil/wax mixtures
No smell after solvent evaporates

So that’s my long story about my quest for a quality finish for wooden tableware, and my initial tests with Tatara/Liquid Glass. I think this seems like a great finish, with a lot of potential. It would be great to bring liquid glass to the rest of the world, and I hope that happens someday. I know there are some similar sounding products being used in Europe (liquid glass nano-coatings, etc.) but I honestly don’t know how those may be similar or different to what’s available here in Japan. If any readers have any insight or thoughts please feel free to comment or reach out through email.

Thanks for reading,

Jon