Met my match with varnish - madagascar copal

[D.W.]

No thanks.

[D.W.]

I edited this post because it got moved. I think making varnishes isn't going to reside outside of hand tool work or possibly violin making, so there's no great reason to leave detail in a forum where more broad finishing talk will go.

I think this isn't a problem (to remove the post), anyway - especially re: the topic. It's difficult, dangerous to make, expensive, and the failure rate would be high. I haven't met a restorer or finisher using resin varnishes at this point. It was perhaps better left off of the forums entirely as a topic due to the obscurity of doing something like not only making your own varnish, but talking about one where failure is a lot more common than success. if that begs the question of why do it in the first place - the answer is imagine a finish that can be wiped or brushed on, that has stability for a couple of hundred years (even in the jar, could be opened 75 years from now and applied and put in the sun and it would cure to usable hardness in a couple of hours), and that is not just durable to typical use where you'd use a polyurethane, but is waterproof and would hold up well even for a few years in the sun outside, is harder than almost any commercial finish, tougher than most, etc, and even though it's expensive, per gallon made at like solids content, would be about the cost of a fine boat varnish with lower toxicity after the cook.

[havabeer69]

do you have this "varnish" or are you asking if there is one?

hard to conceptualise a 100 year old varnish with out... you know... leaving it for 100 years

[D.W.]

do you have this "varnish" or are you asking if there is one?

hard to conceptualise a 100 year old varnish with out... you know... leaving it for 100 years

These varnishes without dryers still exist in bottles. there is a violin maker on maestronet with varnish made in 1940 that can still be applied (and others from the 60s and 70s).

The chemistry of these varnishes is now known and it wasn't well understood 100 years ago. Oxygen, UV light and high heat will catalyze the varnish without adding dryers (heat like baking - like japanning). Without those, or even with just oxygen in the bottle itself from opening and closing from time to time won't be enough to catalyze it.

Point being, you could make one of these types of varnishes and put it in a bottle and it would last next to forever as long as you don't put a catalyst in it. In the old days, those catalysts were sometimes oxides (power) and had to be cooked into the varnish, but stuff like cobalt and manganese (metal salts?) can be gotten in dissolved liquid form and put in at any time. Thus, you can make a jar of something that will last "only five years", or you can really load it up and it may only be good for a year or two, or you can leave the driers out until needed and the varnish itself will be useful beyond our lifetimes.

Well, it's in glass jars because the solvent is turpentine - so I guess there's always a risk the jar will be dropped. That'd end it quickly.

It may not be I guess an obvious thing - what happened with these older varnishes (found by chance from trial and error over a long long long time) that were made of cleaned/washed linseed oil is the linseed oil would polymerize, the tree resin would polymerize, and when cooking the two together, they will crosslink to each other - naturally. When they are later used and cure in oxygen, heat or UV/sunlight - however you use them - they will crosslink further while curing.

I guess we try to manage these things more precisely now - crosslinking when making single-can polyurethane is part of the process, or when using a two part, deciding how much catalyst and what type. Some types of finishes may catalyze naturally without being able to control it, or just due to reaction between components. "real" varnish gets a little better with age, but is stable and won't accidentally set up like this. And some don't crosslink (wax, shellac, nitrocellulose lacquer) at all, I guess.

My oldest varnish is only 6 years old. that would be three lifetimes for some can varnishes, but at 6 years old, it's completely unchanged and certainly has not ever developed even the thinnest of films.

[D.W.]

Actually, I see the owner of this forum did something that was one of my initial questions when I first learned to make varnish. Shellac is wonderful - the melting point is a little low, but the bigger issue on furniture like tables and such is that it's not resistant to water and unless it's really really old and oxidized, it's not crosslinked.

The answer from a varnish sense is it's not similar to a tree resin or natural asphalt in terms of what will just link with oil when it's hot, but I see Ubeaut took a shot at making a crosslinked shellac that is harder (and I didn't read the ad copy, but I would guess, it's also more resistant to water).

And that's pretty cool. I was literally just discussing various "second parts" (crosslinkers) with a chemist, mentioned elsewhere, and supposing that maybe some things we generally use already could be matched up with crosslinking/hardening agents to experiment and see the results. Didn't anticipate someone had already done that with shellac.

[D.W.]

So, this isn't going to be a much traveled topic, I would bet. The term "varnish" in the US is usually either used as a pejorative (granny's orange looking door finish), or it's misused for polyurethane or who knows what else.

But since I have "conquered" madagascar after the initial post describing why it somewhat conquered me, I have put a later light (less crosslinked) madagascar varnish under water overnight - as in, pouring a continuous layer of water on the finish in a cool area where it wouldn't dry fast. that barrier was super thin, but it did degloss a little. To be fair, it cured in the sunlight for a few hours and has no driers in it.

I compared it to some of my other prior efforts, including this brick of congo copal. the congo stuff is just another semi fossilized resin that's thousands to maybe a million years old. It's not that special despite that sounding pretty interesting, you dig in the ground, you find stuff. This is found in one area of the congo and was wildly popular like Zanzibar varnish was before petro finishes.

I don't know the answer yet as to whether or not the best of the petro finishes are actually any better.

At any rate, the test piece just has layers of varnish padded on and it was never put on to be level or anything, just padded on to check color and clarity, so it sits in the shop waiting until the blank is actually turned into a hand plane. that it's super high solids content and dries kind of grainy was known when I padded coats on this test piece, but I've solved it since then (steel wooling between coats prevents it from favoring itself when it dries).

this pile of water is around 5 hours old and most has evaporated. the bit remaining in the middle is question mark shaped because I pushed some aside to see if the finish had deglossed or shown any evidence of water contact at all.

https://i.imgur.com/M0D0Lyb.jpg

none.

I suspect the fact that the middle of the stick looks dark is a camera anomaly around the reflection of an LED light on the top - it's all the same color. The black line divides two regions padded from different batches to confirm there won't be color variation in varnishes that vary slightly in color in the bottle.

I still find it wild that you can take linseed oil and cook it with something that dribbled out of a tree and get a finish like this - no metallic dryers or anything - crosslinking and curing just based on the components that are in it.

The solids % in this finish is almost 70%, but its viscosity is more like what you'd expect out of a 35-40% solids commercial finish. At 35% solids, it runs like water and you can play games with the solvents if you want it to go on level and wet like that and flash off quickly and then finish a little more slowly after most of the thinness flashes off.

The resin itself is $325 for five pounds, so I don't expect it to make a comeback. Cooking it industrially is difficult (confirmed by an Eastman chemist where they had a varnish division long ago), even when you can game it a little with synthetic resins instead of tree resins, and in the early/mid 1900s, the petro and plastics industries saw the opportunity to make a pitch to finishing and chemical companies that hydrocarbon finishes were a better option. I would guess that's enough resin when combined with oil to make 3 gallons thinned. high quality crisp smelling turpentine and higher grade linseed oil factored in with that would mean about $500US for those three gallons. Easy to see why it wouldn't go far industrially.

Phenolic resin like you would see in something like waterlox is about $1-$2 a pound. There is tung oil in it, but the SDS makes it clear that it's more linseed oil than tung, and then the thinners are inexpensive hydrocarbon stuff that's a couple of dollars a gallon.