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Materials and coatings

This is the section closest to our old day job. We formulated water-based inks, polymers and specialised coatings commercially, which means we spent years on the unglamorous end of it: why a batch thickened in storage, why a coating crawled away from one substrate and wetted another perfectly, why two products that should have been compatible were not. Most of what goes wrong with materials is predictable from the chemistry.

Four ideas that prevent most problems

Almost every materials failure we were ever called about came back to one of these. None of them requires specialist equipment to act on.

Adhesion is surface energy before it is anything else
A coating spreads on a substrate when the substrate's surface energy exceeds the liquid's surface tension. Untreated polyethylene and polypropylene sit well below almost every waterborne coating, which is why paint beads up on a plastic tub and why those plastics need flame, corona or plasma treatment before printing. Cleaning matters for the same reason: a fingerprint is a low-energy layer. If a coating crawls, look at the surface before you blame the coating.
Water-based and solvent-based are different technologies, not styles
A waterborne latex dries by coalescence: water evaporates, polymer particles pack together, and the film forms only if the temperature stays above the minimum film formation temperature. Paint applied in the cold produces a weak film that never recovers, even after it warms up. Solvent systems dissolve their polymer and film-form by evaporation alone, which makes them more tolerant of cold and much less tolerant of everything else. This single difference explains most application failures.
Two-part systems fail on ratio and on temperature
Epoxies and polyurethanes cure by stoichiometric reaction, so the mix ratio is chemistry rather than a guideline. Excess hardener does not cure harder, it leaves unreacted material and a permanently soft film. Pot life roughly halves for every ten degrees of warming, and the exotherm of a large mixed mass accelerates itself, which is how a cup of epoxy ends up smoking on a bench.
Storage is part of the specification
Waterborne products freeze and separate irreversibly. Isocyanate components react with atmospheric moisture, so a part-used container has a much shorter life than an unopened one. Dispersions settle and need gentle remixing, never shaking, which entrains air. Peroxide-forming solvents such as diethyl ether and THF develop explosive peroxides on long storage and must be dated when opened. Shelf life on a label assumes an unopened container in the right conditions.

Reading a technical data sheet

The data sheet tells you more than the marketing copy, and a few numbers carry most of the information. Viscosity tells you how it will apply and at what shear rate it was measured. Solids content tells you how much film you get per litre, which is the only honest way to compare price. Minimum film formation temperature tells you the coldest conditions it will tolerate. Pot life and cure schedule tell you how much working time you have. Everything else is usually secondary.

The safety data sheet is a separate document and answers different questions: what it is, what it does to you, what to store it away from, and how to dispose of it. Section 10 on stability and reactivity is the one most people skip and the one that prevents incidents.

What we are building here

Guides in preparation: choosing an adhesive by substrate pair, epoxy systems compared for working time and clarity, surface preparation for low-energy plastics, and a practical guide to chemical storage for small workshops and labs.

If you have a materials problem you cannot place, describe it to us at sales@textinkllc.com. Diagnosing these is the part of the work we enjoy most.