Common solvent/reducer strengths and evaporation speeds

[MMI Enterprises 289]

Link to strengths and evaporation speeds of common solvents used in the painting and staining trades:

ICS on Thinner

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Solvents, Thinners, and Diluents

Solvents, Thinners, and Diluents; What's the Difference?

Not a lot . . .if we're only concerned about liquids that evaporate. However, ask a paint chemist and you will be told that thinners thin or dilute and solvents dissolve other substances.

Water, for example, is a solvent for sugar and salt. That is, water will dissolve sugar or salt. However, water is not a solvent for latex paints . . . it is a thinner or diluent. Water doesn't dissolve the latex resin; it simply thins or dilutes the mixture of paint ingredients. Likewise, water is neither a solvent nor a thinner when mixed with cooking oil. Chemists say the two are immiscible - they don't mix (remember the old adage, oil & water don't mix). Oil won't dissolve water and water won't dissolve oil. In this case, water is neither a solvent, thinner, or diluent.

When paint chemists discuss solvents, they discuss the ability of liquids to dissolve other liquids or powders . . . such as the resin or binder in paint formulations. Paint chemists are also concerned about evaporation rates. If the solvents evaporate too fast, the paint will skin over before it cures. Wrinkles may form or a haze may form on the surface. If the solvents evaporate too slow, the paint will surface cure and trap the solvents inside, resulting in bubbles and blisters.

Evaporation rate and flammability are closely related and the chemist must pay close attention when developing paints for commercial and do-it-yourself use. It only takes a small spark to ignite paints made with fast evaporating solvents.

Paint chemists are also concerned about solvent costs and will often use more than one "solvent" in an attempt to balance expensive solvents with less expensive diluents. The chemists walk a fine line optimizing the paint's performance and cost.

The chemists also consider other performance factors when deciding which solvents to use. They look at flow and leveling, affect on gloss, sag resistance, blush, bloom and haze resistance.

Many of the solvents in today's paints and coatings are derived from crude oil during the refining process. These solvents are often referred to as petroleum distillates. Mineral spirits is probably the most widely recognized "paint thinner" which is refined from crude oil.

The most common "solvents" include: Denatured Alcohol, Lacquer Thinner, Toluene, Acetone, VM & P Naphtha, Paint Thinner, Mineral Spirits, Xylene and M.E.K.

Before we discuss each of these "solvents", we need to talk about strength in a little more detail. Solvents are rated according to their power or KB value. The name - KB - comes from a test known as the Kari-Butanol test which measures relative strengths. The higher the KB the more powerful or "hotter" the solvent and typically the more expensive.

Most of today's paints are supplied as thin or thick as they should be for proper application. However, most labels do give instructions for thinning and/or clean-up. Its important to make sure you are properly informed about thinning paints. If the wrong amount or type of "thinner" is used, the paint will simply not deliver the expected performance and EPA regulations will most likely be violated. Ensure you use the right "solvent" by understanding each product and its recommended use(s).

Denatured Alcohol is ethanol which has been modified with wood alcohol and other solvents to make it unfit for human consumption. Denatured alcohol is a solvent for shellac and a few less widely used natural resins. It may be used as a lacquer thinner, in small amounts, or as a clean-up solvent for paint removers used in wood refinishing. Other uses include glass & metal cleaning or as a fuel for marine stoves.

VM&P (Varnish Makers & Painters) Naphtha is a petroleum distillate which resembles regular Mineral Spirits or paint thinner in strength. A low flash point and fast evaporation make it generally unsuited for air dry solvent borne architectural coatings. It behaves much like lighter fluid and can be used for cleaning up certain residues like masking tape or stickered labels - but be careful of the flammability.

Lacquer Thinner, also a petroleum distillate, is a blend of solvents for use in nitrocellulose lacquers as a partial replacement for the more expensive Toluene. It is also used in some epoxy and automotive finishes, as well as in gravure inks for printing. The mixture is reasonably strong and fast drying. In addition to its stated use, lacquer thinner is sometimes used as a clean-up solvent for "oil-based" products and makes a good brush cleaner.

Paint Thinner or low odor Mineral Spirits is made from petroleum distillates. Mineral Spirits is a general purpose solvent used in the manufacture of most oil-based trade sales paints. It is excellent for thinning oil-based paints, degreasing tools and general household cleaning since its flash point is above 100° F.

Xylene, similar to Toluene, is also strong and fast acting but evaporates at a much slower rate than Toluene. Many oil/alkyd resins are made with Xylene and it is frequently used in aluminum paints to promote leafing. Even though its evaporation is slower than Toluene, it is too fast for most brush applications. Consequently, its use is really limited to paints applied by spray gun and as a clean-up solvent.

Acetone, and other ketones, are not naturally occurring products . . . they are manufactured from petroleum distillates. As a group, ketones are versatile and efficient . . . usually imparting low viscosity very quickly. Ketones are often used in maintenance paints like vinyls, phenolics, acrylates and chlorinated rubber coatings. Acetone is a strong, fast acting solvent, cleaner and remover for inks, resins, adhesives and contact cement. It may also be used as a clean-up solvent after fiberglass projects.

M.E.K. is essentially equivalent to Acetone in power, but is less soluble in water and evaporates slower. It is a strong, fast acting solvent, cleaner and remover for inks, resins, adhesives and contact cement.

Turpentine is derived from steam distillation of pine sap and is the oldest solvent used in coatings. Paints around the turn of the century were made with white lead pigment, linseed oil, Japan drier and turpentine. Turpentine has limited use as it is more expensive than typical solvents. Plus it has a narrow range of solvency and possesses quite an odor. Like kerosene, its use in coatings is very small.

Kerosene is a petroleum distillate that is used only when extremely low solvency and slow evaporation are desired. Possible uses might include paste wood fillers and putties. Old timers incorporated a little kerosene in interior and exterior "oil-based" house paints to supposedly improve brushability, wet-edge and flow by slowing down the over-all evaporation. With today's technology, its best use is as a fuel oil for kerosene heaters, stoves and lanterns.

[Ron Musgraves 240]

Thats some great Info

[Beth n Rod 1,279]

Thanks Kevin!

Beth

[MMI Enterprises 289]

kinda been hidden away eh? Ron always digs back up the good stuff. He like a modern day grave robber/Indiana Jones :)

[Richard 17]

That's a great piece to read. Especialy as I have most of them in stock at the shop.

And to think I got 19% on my grade 11 chemistry exam. My teacher would be proud of me now.

Thanks for bringing it back up.