We all know that wood finishing can sometimes turn out to be tricky, even at the best of times. Hours of work can become ruined when a finish turns out less than perfect.
For example, lets say your shellac finish has turned out exactly as you imagined…except for one thing; it’s pockmarked by little tiny bubbles.
What caused those bubbles? And how do you get rid of them?
Well, in this post you will learn why bubbles appear in shellac wood finishes.
You’ll also discover what you can do to get rid of bubbles in shellac — regardless of whether a shellac wood finish is wet or dry.
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Why Is My Shellac Finish Bubbling In The First Place?
There are two main reasons why shellac bubbles: it either dried too quickly and/or it was applied too thickly.
If shellac is exposed to excess heat, it will fast form into a film. This, combined with the accelerated evaporation of ethanol inside shellac, is the perfect setup for bubbling.
You see, when ethanol evaporates — yet is trapped beneath a dry shellac film — that ethanol will form into little air bubbles.
So while shellac is a conveniently fast-drying wood finish, we don’t want it to dry too quickly all the same. We need to give the ethanol time to evaporate, well before shellac forms a dry film.
But Will The Bubbles In My Shellac Finish Go Away On Their Own?
They should do if that shellac wood finish dries slowly enough to allow them to. Those bubbles will pop all on their own — but only if that shellac coat has been applied thinly enough.
If shellac is applied too thickly, this can also create a trapped-bubble effect in this finish too.
Related Post: Is Shellac A Good Finish For Outdoor Furniture?
So What Can You Do To Get Bubbles Out Of Shellac (While It’s Still Wet)?
You can try a wood finishing technique known as ‘tipping off’.
When you tip-off a wood finish you are simply using your brush to ‘press’ those bubbles out. This requires a light touch though, as it involves lightly sweeping the very tip of the brush bristles along with the grain.
Having said that, tipping-off is a little bit of a coin-flip as to how effective it is at getting rid of bubbles (especially in thickly coated wood finishes).
Nevertheless, if you follow a couple of key steps, tipping off should be enough to get rid of the bubbles:
Step 1). Always Use A Clean Bristle Brush
The brush you use to tip off shellac should be clean. Basically, it should have no shellac on it.
On top of that, bristle brushes (particularly natural bristle brushes), can have little pockets of air in those bristles. And if you’re not careful, that brush could add more bubbles to your finish, rather than smooth them away.
So, make sure you dip the brush in mineral spirits first — and then squeeze off any excess — before you begin.
Step 2). Keep The Pressure Very Light
You need to keep things light as you move the brush with the grain. There should be very little downward pressure at all.
In fact, if the bristles of the brush begin to bend, then that’s a sign that you’re pressing down a touch too hard.
Related Post: Can You Put Shellac Over Paint (Best Practice Revealed!)
Got It…But Is There A Way To Get Rid Of Air Bubbles In Shellac After It’s Dried?
If those bubbles look like they are there to stay, then you can try removing them from shellac using ethyl alcohol (a.k.a denatured alcohol).
This high-proof alcohol is what we use to break down shellac flakes in the first place. So, a rag dampened with denatured alcohol — then lightly swiped over shellac — will dissolve and smooth away bubbled sections.
Afterwards, you can apply shellac once more onto the surface to even it out.
Related Post: Thinning Shellac With Mineral Spirits Won’t Work (Here’s What Will)
To Wrap Up, Here Are The 3 Key Takeaways From This Post…
- 1). Air bubbles in a shellac finish are often the result of a shellac coat drying too quickly. The ethanol inside this finish evaporates and becomes trapped inside that dried shellac coat.
- 2). Another reason for those bubbles can be due to application. If you apply shellac on too thickly, this can cause uneven drying, leading to air bubbles becoming trapped.
- 3). You can remove air bubbles in a still-wet shellac finish by tipping off the finish with a bristle brush.
Shellac/nanoparticles dispersions as protective materials for wood. Appl. Phys. A 122, 1058 (2016) – Springer.com