Solvents

Where a surfactant lifts soil off a surface, a solvent dissolves it, and the two together do things neither does alone.

What a solvent adds

Dissolving power for soils water cannot touch: inks, adhesives, waxes, heavy grease.

Faster evaporation, which is what makes a glass cleaner streak-free.

Coupling, holding a formula together when oil-loving and water-loving components would otherwise separate.

The usual ones

Ethanol and isopropanol, for glass and fast-drying products. Flammable.

Glycol ethers, the workhorse of heavy-duty degreasers: strong, water-miscible, and the family with the most varied toxicology, so the specific one matters.

d-Limonene and other terpenes, which smell of citrus, degrease well, and are aggressive towards plastics and towards skin.

Glycols, as humectants and coupling agents, low volatility.

And methanol, which is worth naming because it carries a child-resistant packaging requirement at 4 percent or more.

Flammability is the constraint

Solvent content decides the flash point, and the flash point decides how the product is labeled, stored, insured and shipped.

A flammable liquid brings DOT requirements for transport, which reaches parcel shipping and can mean a product cannot go by air at all.

It also reaches your own workspace: quantity limits, ventilation, ignition sources and your insurer's view of what you do.

Which is why a high-solvent product is a different business from a water-based one even at the same sales volume.

What they do to the bottle

Solvents are the main cause of container failure in this category.

They swell and craze some plastics, permeate slowly through others, and attack trigger seals and dip tubes while leaving the bottle intact.

Terpenes in particular are hard on plastics and on the elastomers in a sprayer.

So a solvent decision is a packaging decision, and the compatibility test is not optional for a solvent-bearing formula.

References