Blotchy Mottled Shellac Finish

Hi all.

I’m having a bit of a problem with a shellac finish I’m applying to some jarrah drawer fronts and was wondering if anyone might be able to provide any hints to what the problem may be.

I’m aiming for a shellac and wax finish but am getting a very mottled/blotchy surface in the shellac finish that I’ve never seen before. I normally just see slight tracks from the overlapping brush strokes which is easy to rub back.

I’m using Ubeaut white shellac (in date) applied with a good camel hair mop. I sanded to 1200, applied one coat diluted 5:1, sanded lightly with 1200. Then used 50/50 mix for 3 more coats.

I can’t quite remember if the finish was mottled at this point, but I cut it back with W&D paper with water and a little detergent. But obviously 3 coats of 50/50 was too shy and I went through to bare timber in some points. So start again. More coats this time, but I got the blotchy effect shown in the photo below. I thought one cause may be that I didn’t properly wipe all detergent residue from the surface, so I sanded back to get all blotchiness off (only to bare wood in some spots), cleaned thoroughly with plain warm water, sanded 1200 and then applied 5 coats of a thinner cut this time. Same problem. I used this exact technique for the rest of the cabinet a while ago with no problems. :?

Any ideas or help would be much appreciated?

Cheers,
Gibbo.

Hi Gibbo,

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Chipman


Ah, Now I see them...

Is it possible the water made the grain swell? I am not an expert with shellac but I would have thought you should avoid water... use dry paper or steel wool between coats and you can use a rubber to flatten the surface. I hope some guys who really know can help you as it is obviously disappointing

You didn't happen to mistakenly dilute it with turps or something else instead of metho did you?

Was it raw timber or had it been stripped?

What preparation did you do before applying the shellac? Sanded to 1200 as you said but what else?

Did you use EEE prior to the Shellac?

Had it previously been oiled or has there been any welding done nearby like within 100 meters?

If on new raw timber has it been kiln dried or air dried?

What soap did you use as a wetting agent in the water?

It looks like a reaction to wax or oil something else on the surface of the timber. Possibly a problem with the soap used in the sanding, if the surface wasn't washed off well with clean water and dried properly.

My bet is a contaminant of some sort on the surface or mistaken dilution with the wrong solvent.

Cheers - Neil :)

did you leave enough drying time between each coat?

i had a similar looking thing a few years back while restoring a table and it did turn out to be the wax previously used on the table.

Quote:

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Had it previously been oiled or has there been any welding done nearby like within 100 meters

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i found this intresting... what effect dose it have?

km

Thanks very much for your replies.

Chipman - thanks, it certainly was disappointing. I used the water for sanding after the finish had dried overnight to cut it back which I believe is ok (according to Neil's book). I might try the steel wool and rubber idea :)

Neil,
I did use metho and not turps - Brinlays metho which has marked on the front 100% hydrocarbon. Does this mean it should be IMS? I should do your turps test for water.

The timber was raw. Didn't use EEE before shellac, but will at the end. Hadn't been oiled. I'm not sure as to how it was dried. The drawer fronts used timber from two different suppliers, and both have the same problem, so I'm guessing it's not the timber's fault.

Preparation - On raw timber after sanding to 1200, I wiped surface with a clean rag & metho to raise grain, then very brief sand with 1200. Wiped surface down with clean rag (probably should have used a tack cloth). Then started the 5:1 sanding sealer coat and the rest. For the sealer I did use some dewaxed white shellac with 2006 use-by date, but then moved on to in date stuff for the proper coats. Is this OK?

There was no welding. What effect does this have?

The soap I used was Palmolive original dishwashing liquid - a squirt in water, and I dipped the paper in it before sanding.

BillyM - I left about 20mins between coats. It wasn't tacky at all - is this enough?

I must have got some contamination in there somewhere. So the big question is how do I fix it - do I sand right back to bare timber, carefully clean out brush and containers and start again?

Thanks for your help! :)
Cheers,
Gibbo.

Gibbo. you don't say what you used to dilute to 50\50, I wondered if you were not melting the bottom coast and your brush is causing an amalgamation of both coats .Don't know for sure.:? Is your brush them same one used earlier?

I did use metho and not turps - Brinlays metho which has marked on the front 100% hydrocarbon. Does this mean it should be IMS? I should do your turps test for water. If what you used to thin etc is 100% hydrocarbon it is definitely the wrong thing. Hydrocarbons are basically oil derived eg Turpentine, methanol (hope it's not methanol) etc. Methylated Spirits is alcohol. Hopefully you have just got mixed up with what's on the label. If not get rid of it as it is definitely the wrong thing.

The timber was raw. Didn't use EEE before shellac, but will at the end. Hadn't been oiled. I'm not sure as to how it was dried. The drawer fronts used timber from two different suppliers, and both have the same problem, so I'm guessing it's not the timber's fault.

Preparation - On raw timber after sanding to 1200, I wiped surface with a clean rag & metho to raise grain, if the metho wasn't metho this could be the start of the problem then very brief sand with 1200. Wiped surface down with clean rag (probably should have used a tack cloth) Clean rag is fine. Then started the 5:1 sanding sealer coat and the rest. For the sealer I did use some dewaxed white shellac with 2006 use-by date, but then moved on to in date stuff for the proper coats. Is this OK? Out of date stuff should be fine for Sanding Seal 8:1 would be a better mix for this but shouldn't hurt as it's basically sanded back off again before you begin. You did sand it off didn't you? The idea of SS like that is to raise the grain as you did with the metho then sand it off with your finest grit.

There was no welding. What effect does this have? Silicon from welding rods can travel a few hundred meters on a still day and with a very light breeze, even further. Would have looked more like pock marks if it was.

The soap I used was Palmolive original dishwashing liquid - a squirt in water, and I dipped the paper in it before sanding. Couple of drops in an ice cream container would probably be fine.

I left about 20mins between coats. It wasn't tacky at all - is this enough? If your coats are heavy you probably need more time between coats as the top one will eat the bottom one away, but that really doesn't look like the problem here. It definitely looks like some sort of contamination either of the shellac or the surface or possibly the brush. My guess is still with the solvent or something on the surface. Fly spray, CRC or similar sprayed in the region of the finishing could do this even contaminated rag which may have been used for something else or dried in a cloths dryer with fabric softener could possibly do it.

Bit of a conundrum, eh.

Check out that solvent before anything else and let us know what it really is.

Cheers - Neil :)

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Originally Posted by ubeaut

If what you used to thin etc is 100% hydrocarbon it is definitely the wrong thing. Hydrocarbons are basically oil derived eg Turpentine, methanol (hope it's not methanol) etc. Methylated Spirits is alcohol. Hopefully you have just got mixed up with what's on the label. If not get rid of it as it is definitely the wrong thing.

Check out that solvent before anything else and let us know what it really is.

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Ah, bummer! Check out the photo - label clearly says Methylated Spirits, but underneath says "contains 100% hydrocarbon"). I've been had! :doh: A trap for the uninformed public. I wonder what it really is...

Will stripping back to bare timber and starting again with real metho work, or have I contaminated too far? It does smell like metho though.

billym - I was using the same camel hair mop for all of it, but you may be right - looks like I need to wait longer between coats as well.

Thanks heaps for your help guys! You may have saved me from much more future frustration!
Cheers,
Gibbo.

Stripping back and starting from scratch should work.

Get a new bottle of metho, new (current date) shellac, discard the thinned shellac and give the brush a really good wash with the new meths.

Start from scratch with a 8:1 metho Shellac mix as the sealer, sand with your finest grit, then go for it. Fingers crossed it should be fine.

Not entirely convinced what's in the bottle isn't metho either. It may just be mislabelling, but looks like there are a heap of mislabelled bottles out there if it is.

You do realise there are restorers and repo people who would almost kill for the finish shown in the pics.

Cheers - Neil :U

Thanks very much for your help Neil. :2tsup:

I'll strip it back, follow your advice and cross my fingers. :)

Cheers,
Gibbo.