Shellac - finishing disaster

[Darius Ferlas]

I finally got around to using Zinsser SealCoat, which is de-waxed clear shellac. I was supposed to live happily thereafter. That kinda didn't work out that way.

I read around the forums how wonderful shellac is and how easy it is to apply and bring to a nice uniform shine. I did come across a warning somewhere on SMC, that newbies should start their adventure with shellac by using a 1 lb cut, so I thinned the shellac I bought. The batch was dated 2009 so it still has about two years of shelf life, as per Zinsser specs.

First the problem started with the application. Brushing yielded rather significant witness marks so I decided to sand those out. I let the shellac dry very well and next morning I started to sand the surface with 120 grid to get rid of the overlaps. I noticed tat my ROS started gumming some spots up. So I decreased the grid (down to 80) and that seemed to have helped. My next step was re-coating with an even thinner shellac. The result was nowhere near the museum quality but it was much better than brushing. At least some of the faint smudges seemed thin enough to be taken care of by some 100G sanding. Again, gumming up. I went down to 60, then 80 and ended up at 150.

That's when I decided to apply a coat of Pratt and Lambert #38. The varnish is astounding and unbelievably easy to use but... I got blotchiness, which I assume is from a thin but gummed up shellac.

I am considering various options, one being complete stripping of both finishes with a more aggressive grid (40, or even 36), then working my way up to 150 again.

I am attaching a photo of the disaster. The rightmost darker spot is intentional, I know, that little heart shaped pair of knots is a bit tacky but wifey likes it. The blotchiness is mostly the large, darker spots along the center line of the table and within the left bottom corner around the breadboard area.

Help!

[Prashun Patel]

From here it doesn't look like a disaster.

One thing to know about shellac is that since each coat fuses with and melt into the previous coats, there's no need to sand so hard between coats. Certainly, there's no need to go to 120 down to 100 down to 100 and down to 60! Sanding between coats should be in the 220-320 range just to remove nibs.

To remove the ridges you mention - and I get them too - the best is to use an alcohol dampened rag / pad to melt and smooth out the ridge. You might mess up any sheen you have there, but you'll be able to get that on the next coat.

That brings me to the next point: don't work the surface by painting it many times. Don't lay down a thick coat like with varnish. If you have uneven or brushy strokes, have the discipline to let it be and to fix it on the next pass. After a few coats, it tends to even out - magically.

Padding is also always an option. You can do it 'properly' by making a 2-layer pad, but frankly, I'm able to pad it on good enough with a quarter piece of a shop towel folded a few times. *Don't dip*. Squirt a little shellac onto the rag (this is the reason why padding works). Wipe across the piece until it runs out, then squirt more. Because you are putting so little on, it dries super fast, and does not drip, so by the time you get to the bottom of yr piece, you can put on another thin coat from the top. Keep doing it until yr rag/pad starts to drag. With a properly formed pad, you won't have to reload or "charge" it so much. With my shop towel, you're basically constantly charging every foot or so. However, with a squirt bottle, it's easy. In fact, when you get the feel of swiping, you'll be able to even squirt a little right on the table, and just wipe it in.

The big key w shellac is not trying to get a perfect sheen. Just focus on not getting nibs and runs, and trust me, after several coats, your even sheen will magically appear. Don't try to get a thick or built up coat. With each subsequent coat, yr not so much putting on more material as you are just trying to fill in gaps and blend everything evenly.

Saying shellac is easy to apply is a bit misleading. What people REALLY mean is that it's easy to FIX mistakes on the next coat.

Sorry for the ramble...

[Mike Null]

With all the problems mentioned I am still a big fan of shellac. In most cases I prefer to spray it but even when brushed I don't use coarse grit paper. Sometimes a little steel wool and dna will work wonders.

[Darius Ferlas]

Shan, thanks for the reply.
Right now I am beginning to understand the mistakes I made while applying the shellac. Too much, too slow, too much overlapping and with the humidity being low. My initial attempts to sand out some overlaps out were with higher grids but since that didn't seem to be of any use I went down to more aggressive grids.

At this point I decided I need to strip the finishes down to bare wood and start again. It looks like I have tried to bite more than I could chew, especially on a large surface like that table.

Luckily, the varnish was still wet when I took the picture in my post above. With mineral spirits it was pretty easy to wash the coat away, hopefully all of it.

Right now I am looking for the best way to remove the shellac. Would then denaturated alcohol be the way to go, aggressive sanding or a combination of the two?

For better clarity of why I think the finish is a disaster I took additional shots zoomed on the blotchy areas. They do stand out and certainly look like there is a finish problem there. With the glossy varnish atop the wood it looked even worse.

Mike, what is dna?

[Joe Chritz]

DNA is denatured alcohol short hand.

If you are using a wiping varnish why use the shellac at all?

Shellac is very easy to spray, everything else is a bit harder. It is a put it down and don't touch it thing. You do not have the forgiveness of a slow drying oil varnish.

You weren't using that foam brush for the shellac were you?

Joe

[Faust M. Ruggiero]

Joe,
Here are two consoling thoughts. First, you can strip and re-apply a finish. In fact, lots of finishes like being applied over shellac. Make sure you remove as much as possible and sand really well.
The second consoling thought is this. Some of the best finishes I've ever seen were second finishes done over a poor first effort. You are armed with more knowledge than you had during the first attempt and the wood is now well sealed. The next one will be great.
fmr

[Prashun Patel]

Your finish probably isn't responsible for the blotch. The blotch is a function of the wood and the preparation. In fact, many people recomend using shellac precisely as a blotch preventer.

To what grit did you sand BEFORE you applied anything? Did you color the wood with anything? Doesn't look like it.

[Michael MacDonald]

DNA is denatured alcohol short hand.

If you are using a wiping varnish why use the shellac at all?

Shellac is very easy to spray, everything else is a bit harder. It is a put it down and don't touch it thing. You do not have the forgiveness of a slow drying oil varnish.

You weren't using that foam brush for the shellac were you?

Joe

so are foam brushes bad for applying shellac? I have used them recently, and thought they were OK... I saw shawn's approach described, and may give that a try... prior to the foam brushes, I was using natural brushes and didn't like it...

[Darius Ferlas]

Joe,

spraying is not an option for me at this point. I may look into it after I get some other shop equipment priorities taken care of. I didn't use the foam brush for the shellac but I did use it for the varnish and that part worked beautifully. Also, Zinsser lists foam brushing as one of the acceptable options for this product.

Faust,

I am indeed trying to see the glass half full here. A little extra sweat and the delivery schedule postponed. I do want to figure this shellac out as I appreciate its aesthetic and chemical value since, at the very least, it affords a wider range of compatibility between finishes.

Shawn,

In a way I feel you are right, the finish material was not responsible for the blotching. My inexperience was. The blotching occurred in the general areas where I remember some of the gumming up to have occurred. Before I applied the shellac the whole surface was originally sanded following this schedule: 60, 80, 120, 150, 180, 220. I applied no coloring to the wood, or to the finishes at all.

The varnish is stripped so now I have even more questions:

1. Any tips I should be aware of for washing out shellac with DNA?
2. Will the glued joints be affected? (I used TB III)
3. I read somewhere that turpentine would retard the drying of the shellac, but I am unclear about how much turpentine to add, what drying times to expect etc.
4. if turpentine is not such a great option, would then some DNA or other alcohol be a good thing to use in lieu of sanding paper to knock down any ridges?

Again, I appreciate all the responses.

Darius

[Steve Schoene]

Some comments. First lets start with your numbered questions.

1. You don't really need to remove all the shellac, just remove enough so that if any remains it says smoothly without defects.
2. No, it won't affect the glue.
3. Yes, it will, but I wouldn't. Shellac can be easily enough made to work just fine without that. I'd persist a little.
4. Adjusting your technique in applying the shellac is the easiest. A little sanding with 320grit --by hand, NEVER with ROS--should be plenty.

Now some things about wood preparation. If your wood has pased through a planer, or been straightened on the jointer, there should absolutely be no reason to be using 60 or even 80 grit sand paper. They just put in large scratches that take lots of work to remove. If you are applying any film finish, then sanding to 180 grit is generally all that is needed, but there is no harm in 220. If you use an ROS for most sanding, remember that you should finish off by hand sanding with the grain, using the same grit as your final ROS grit.

As far as applying shellac. Shellac must be applied quickly and confidently. You can't apply shellac and then brush in out like you might with varnish. Padding is generally the most forgiving. Keys to success are to work quickly, never go back to get a missed spot, and the instant you feel any drag of the pad (or brush for that matter) STOP.

I don't like ordinary brushes of the sort you might use for varnish. They lay down too much shellac and don't do it enenly enough. For brushing I much prefer a fine sythetic bristled waterclor wash brush from an art supply store. (Taklon gold bristles are good.) These brushes don't carry much shellac--you do have to dip them a lot, but, they leave no brush stroke marks. I brush on a thin stroke. Then when I start a new stroke I begin a shy inch from the end of the last, brush toward to previous stroke, and then immediately stroke back the other direction. The ONLY spot that is ever touched twice by the brush is that first inch. That prevents "lump" where the brush touches down. In general, if there are small lumps or missed spots the next coat will deal with that as long as you don't skip the same place again.

You need not sand between coats of shellac unless there is some screw up you want to fix. And then you only need 320 grit by hand.

When you have build a sufficient film of shellac then you can complete the process by rubbing out the surface to remove any defects and achieve whatever gloss you want. Shellac doesn't need a thick coating, but get enough so you can sand out defects and rub to the desired sheen without cutting through. For rub out I start with 600 grit (400 if defects are larger), and then jump directly to 1200 grit, or 2000 grit if I am going to gloss. When all the 600 grit scratches are removed, I then use rottenston to achieve a glossy finish or pumice to achieve a satin sheen. Polishing compounds work well too.

[Neal Clayton]

so are foam brushes bad for applying shellac? I have used them recently, and thought they were OK... I saw shawn's approach described, and may give that a try... prior to the foam brushes, I was using natural brushes and didn't like it...

i can't think of anything those foam brushes are good for.

i use a regular ole BORG china bristle brush. no need to use a really good brush, it won't make that much difference since it dries so fast.

same way you paint anything else. saturate the brush, shake out the excess, full-length strokes overlapping as little as possible.

also, i know that zinnser claims to be able to preserve shellac longer than normal with additives, but i wouldn't use a can older than 6 months. it does have a shelf life. won't affect the appearance that i know of, but will hinder it from drying if it's too old.

[Steve Schoene]

Zinnser doesn't use additives to extend the shelf life, it is more what they "take out or alter " in the processing. I'd also be a bit sceptical of the stated life, though it depends on the application as to what is "fresh enough"

[Prashun Patel]

i use a regular ole BORG china bristle brush.

Interesting. never tried that; I always used a synthetic brush, thinking china's reserved for oilbased finishes.

[Neal Clayton]

Interesting. never tried that; I always used a synthetic brush, thinking china's reserved for oilbased finishes.

ironically, the best brushes i've found for brushing shellac on existing wood moldings, which of course has some vertical and upside-down surfaces, are these. 12 bucks at the borg. and yea, they're the ones typically marked as "for oil paints". i think the softer white china bristles help with not pressing too much shellac from the brush. the stiffer black bristled ones seem harder to control for me.

here's a normal, hi-res, and from-a-distance on a wide doorframe finished with garnet using the above cheapo borg purdy brushes. you can see some faint brush lines in the glare on the close up pic, but i think it's good enough for gubment work . probably would need buffed/polished if it were furniture, but for my purposes it's plenty good enough without much effort.

[glenn bradley]

Sorry you had that experience. Shellac is my "go to" finish. I always use a pad. First coat is generally a 1lb cut unless am just using it as a barrier or sealer; then I'll thin even more. Second coat (and any more, if required) are 2lb cut (Zinsser out of the can).

Things that work for me:
1. - pad the shellac on:
==> for large surfaces I use a cheese cloth wad inside a smooth cotton wrap; otherwise, folded paper towel pieces.
2. - never go "back over" an area:
==> any goofs will vanish with the next coat 30 minutes later following a 320 - 400 grit de-nib if required.
3. - do not try to apply a thick film as with a varnish:
==> shellac does not "level out" like other top coats; it sets too quickly (at least in SoCal).

I would urge you to try again on some test pieces. You may find it to be a very useful element in your finishing arsenal.