General Information Regarding Epoxies

This information is not specific to Smith & Co Oak & Teak Epoxy, but is certainly applicable. It is direct information from Steve Smith, the “Smith” of Smith & Co. See: https://www.glueoakandteak.com/

MIXING TWO-COMPONENT PRODUCTS

Sophisticated adhesives, sealants and coatings are two-component systems. One part has to be mixed with another part before they are applied. After a while, a chemical reaction takes place and what is created is a filler, paint or glue with exceptional properties. It is not possible to obtain those properties by taking some simple thing out of a can.

Each of these two parts, whether they are liquids or pastes, consists of very small parts called molecules. The manufacturer designed the system so that the individual molecules of each component would react with each other in certain proportions. That is why the instructions say to mix the materials in those proportions.

If the materials are mixed in different proportions, then some molecules of one-or-another component will not be used. They are left over, scattered among the molecules of both components that did react together. In that case, the material will be softer or weaker than it should be, or will soften in water when it should not. It might be a gooey mess. It is therefore important to mix the components thoroughly, so that everywhere in the mixture the ingredients are in the correct proportions, even down to the individual molecules. If the materials are portioned-out properly but not mixed thoroughly, then we will have too-many A-type molecules in one place, and somewhere else we will have too many B-type molecules. The net result of that is TWO places where it will not cure properly.

For example, we make the components A and B of our Fill-It Epoxy Filler to be different colors, so it will be easy for you to thoroughly mix the product. When you can see the streaks of different colors you know you must continue to smear, scrape, fold and mix until the color is uniform. The mixing tools themselves must be scraped occasionally. If mixing a paste on a flat surface, the mixing surface itself must occasionally be scraped off and the mixture folded-over itself a few times and then the smearing-and-scraping-and-folding mixing-action continued.

Our glues are all clear liquids, so even though one is colorless and the other amber, it is not always easy to thoroughly mix the liquid components. Here's how to do it: Measure out equal volumes of the two components into one container. Mix thoroughly in that container, scraping off the mixing-stick on the edge of the container occasionally. Then scrape out the entire contents into a second container and mix all-over-again. If you are not sure you got it all mixed, scrape everything into a third container and mix again. In this manner, the unmixed bits near the bottom corners of the first container become right-in-the-middle at the top of the second container, and then the entire mixing process can be really complete. If thoroughly mixed right down to the level of the individual molecules, the product will cure into the high-quality glue or filler it is supposed to become.

If there are any soft or gooey spots in the final cured product, that actually proves the material was not thoroughly mixed. I know you want to get good results; the foregoing is how to get that, with mine or anyone else's products.

DURABILITY OF GLUED WOOD

Wood expands differently it in its three dimensions: axial, radial (quartersawn) and tangential (plainsawn).

Joint design and the relative (meaning differential) expansion and contraction between different pieces of wood determine the shear forces generated across the bond-line, whether due to temperature variations or wood moisture content variations.

Ideally, wood should be conditioned and glued at the atmospheric moisture-content where it will see service, meaning in some cases built-where-it-will-be-used.

Thicker glue lines will absorb more shear displacement.

Eventually, the shear strength of the wood itself is the limiting factor, as softer woods may shear next-to-the-glue-line and wet wood has a much lower shear strength than dry wood. That is a very good reason for joints to be glued-and-screwed.

It is critical that surfaces to be glued be sanded first, to ensure the removal of even a very thin, colorless film of Mill Glaze.

Cure times vary with temperature; chemical reaction rates double roughly every 18 F degrees. While in most cases the joint will be able to be unclamped and handled the next day (warm weather) or in 2-3 days (cooler weather); ultimate cure proceeds more-slowly with every further increment of time; example: in my lab 60% cured (decent handling strength) in 16 hours, half-way-further in another 24 hours (meaning 80% cured, 20% uncured), half-way-further in another 24 hours (meaning 90% cured, 10% uncured), half-way-further in another 24 hours (meaning 95% cured, 5% uncured), and you can see that's why folks that make this-kind-of-stuff say "ultimate properties will be obtained in a week-or-two". It's how long it takes for the glue adhesion-strength and glue-polymer-strength to get up to the shear strength of the wood, whatever-that-happens-to-be.

I've had folks use my Oak and Teak Epoxy Glue and its earlier versions going back to the early 1970s in climates all-over-the-map on a wide range of woods and had excellent results.

Smith's Epoxy Cleanup Solvent™ will dissolve and clean up any epoxy glue before it has gelled. Once cured, there is no cleanup solvent.