Slow Drying Finish Solutions | Popular Woodworking Magazine

Why stains and finishes generally dry slowly.

A buddy known as with an issue. He had utilized an ebony oil stain to oak and after the stain had dried for 2 days, the polyurethane he then brushed picked up a few of the colour and smeared it across the floor.

Was there an issue with the stain, or did he do one thing improper?

Well, I might consider a number of attainable issues with the stain. First, a really darkish stain requires extra pigment. So possibly the producer simply hadn’t added sufficient binder (oil or varnish) to encase all of the pigment properly. Second, some producers are changing solvent with slow-drying oils to adjust to California VOC guidelines after which promoting this product to the whole nation to keep away from having to make two strains. Oils dry slower.

But my first thought was the climate. Though it had been delicate currently, with highs within the 60s and lows within the 40s and 50s, that’s nonetheless too cool for regular drying. Most stains and finishes want a minimum of 65° to 70° temperatures for eight hours or extra to dry at a standard charge. (Exceptions are water-based stains and finishes, that are affected extra by humidity than temperature; and lacquers, which might be made to dry usually in chilly climate by including acetone or fast-evaporating lacquer thinners out there from auto-body provide shops.)

So I requested in regards to the store temperature whereas the stain was drying. My buddy assured me he had warmth, however on additional questioning he revealed that he turned it off at evening.

After attempting the stain myself in my heat store, I concluded the issue was lack of enough warmth. This is often the reason for stains and finishes drying slowly, and it’s the very first thing you must consider when confronted with a drying drawback.

If you’ll be able to’t keep away from a chilly store you could possibly convey the mission inside your own home after every coat, or you could possibly maintain the end heat with a warmth lamp or perhaps a blow dryer for small objects. Alternatively, you’re simply going to have to provide every coat longer to dry.

Temperature isn’t the one reason for gradual drying. Others embody:

• Applying oil or varnish onto oily woods;

• Not wiping off all extra oil end; and

• Using shellac that’s too previous.

Oily Woods

Oily woods. The oily resin in some woods slows the drying of oil and polish finishes, so you must take away this resin earlier than making use of both end. Acetone is the simplest solvent for elimination, however it may raise a few of the colour and smear it over different woods in case you are utilizing a number of hardwood species collectively, as I’m doing right here. Mineral spirits and naphtha gained’t do that, however they’re much less efficient at eradicating the oily resin.

Most unique woods, resembling teak, rosewood, cocobolo and ebony, comprise pure resins that really feel and act like oil. These resins retard the drying of oils and varnishes (and in addition oil stains).

This is counter-intuitive – a lot in order that it’s widespread to see directions in woodworking magazines calling particularly for the usage of oil or varnish on oily woods as a result of these finishes are “compatible.” The reverse is the case. Oils and varnishes are the one finishes that don’t dry properly.

The clarification is that this: The non-drying oily resins on the wooden’s floor combine into the moist oil or varnish end and maintain the end molecules aside so that they don’t stumble upon one another and crosslink. The resins act like paint thinner that doesn’t evaporate.

Once you’ve gotten utilized an oil or varnish to an oily wooden and found the end isn’t drying, there are solely two good fixes: apply warmth to the floor to excite the molecules so they’re extra prone to stumble upon one another and crosslink, or strip the end and begin over. It’s often fairly simple to strip (really simply wash off) an oil or varnish that hasn’t dried utilizing naphtha or lacquer thinner. Sometimes mineral spirits is robust sufficient.

To forestall a drying drawback earlier than it occurs (or after you’ve gotten stripped a non-drying end), take away the oil from the floor of the wooden or seal the wooden with shellac.

Sticky oil. You ought to all the time wipe off all oil end from the wooden after every coat. If you allow the wooden a bit of damp, as I’ve carried out right here, the end gained’t dry properly. It will stay sticky for days, or longer.

To take away the oil, wipe with one among a number of solvents: mineral spirits, naphtha, alcohol, acetone or lacquer thinner. Mineral spirits and naphtha are the least efficient, however they don’t raise and smear the colour of the wooden. Each of the opposite solvents might take away a few of the colour together with the oily resin.

So when you’ve got joined two or extra woods, as in a chopping board or segmented bowl, strive mineral spirits or naphtha first. Check that the colours don’t smear on scrap wooden earlier than utilizing one of many different solvents.

Whichever solvent you employ, moist the wooden properly with one rag then dry the wooden with one other so that you take away the oil, not simply smear it round. Apply the brand new end proper after the solvent evaporates so there’s not time for the oily resin within the wooden to rise again to the floor.

Alternatively, you’ll be able to seal the wooden with one other end earlier than making use of the oil or varnish. Shellac is the simplest at blockading the oil.

Oil Finish

Undissolved shellac. Bleached shellac loses its potential to dissolve after just a few years. If the shellac appears like this, even after in a single day in alcohol, it’s no good and must be thrown away. The “blocked” flakes to the left of the jar are a very good indication that the shellac could not dissolve.

The widespread instruction for making use of oil and oil/varnish-blend finishes is to moist the floor properly after which wipe off the surplus after the end has had a couple of minutes to soak in. This instruction is obscure as a result of totally different interpretations might be given to “wipe off the excess.”

What is supposed is ALL of the surplus. The floor shouldn’t be left damp to the contact. Oil doesn’t dry properly, so leaving even a really skinny movie of damp end (something that wets your fingers or feels sticky) will end in a sticky floor for a very long time.

If you’ve gotten a state of affairs the place you didn’t take away sufficient of the oil and it’s now too sticky to take away with a dry fabric, observe the directions above for coping with an oil or varnish that gained’t dry on an oily wooden.

Shellac

Slow drying shellac. Dissolved shellac deteriorates because it ages in order that it dries slower and loses its water resistance. This is the rationale you must use shellac as freshly dissolved in alcohol as attainable. Here, my finger nonetheless leaves a mark within the shellac after in a single day drying. The shellac was 5 years previous.

Shellac deteriorates way more quickly than different finishes. The deterioration results in slower drying and lowered water resistance.

In stable flake kind, bleached or “blonde” shellac deteriorates a lot sooner than non-bleached, generally inside a 12 months or two (non-bleached stays good for a few years). The variables are the strategies used to bleach the shellac and the temperature through which the shellac is saved, with greater temperatures resulting in sooner deterioration.

You can gradual the deterioration by storing the shellac in a fridge.

Once the shellac is dissolved in alcohol, all sorts of shellac deteriorate, once more with this occurring sooner the upper the temperatures through which the shellac is saved. You ought to use the shellac inside a 12 months of its having been dissolved in alcohol in case you are utilizing it as a end and never simply as a sealer beneath one other end.

For any vital mission, resembling a tabletop, you must dissolve your individual flakes and use the shellac as rapidly as attainable – inside a number of weeks or months.

Other finishes additionally deteriorate, in fact, however the deterioration doesn’t result in considerably slower drying. Pre-catalyzed lacquer loses a few of its sturdiness after just a few years (the time varies with totally different producers), and water-based finishes generally curdle after quite a lot of years. I’ve by no means seen varnish or lacquer deteriorate so long as air is saved out of the can, irrespective of how previous.