Hairdryer vs polyurenthane - day 1 (Full Version)

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mrstwinkle -> Hairdryer vs polyurenthane - day 1 (Jan. 21 2018 20:00:18)

This is a laugh at the amateur thread. I deserve all the mocking that will ensue. Diary of me trying to remove a thick coat of polyurethane. First photo attached - 10 mins of hairdrying in. I'd bought a cabinet scraper but it is too big and too harsh so I'm just using thumbnail to pick bits off.

Before someone beats me to it.... I'm well aware that
A I might undo the glue inside
B I might trash the wood
C This is crazy



jshelton5040 -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 21 2018 22:36:40)

What brand guitar is it? If it's a cheap factory guitar just get out your orbit sander.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 7:30:57)

Valeriano Bernal 1982



estebanana -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 7:38:22)

Get some paint stripper. The stripper that you get now is not as powerful as the old jasco stripper. But the trick is, put it on thick and put aluminum foil over it and tape down the edges. Let it sit on there wet for a few hours and check it. Sometimes several hours are needed with the newer environmental safe paint remover.

You're working too hard. Let the remover do the work, then scrape off the finish.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 9:43:27)

I'd read several guides suggesting unlike other varnishes, polyurethane is difficult/near iimpossible to penetrate with chemicals.

Experience to the contrary would be interesting?



jshelton5040 -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 14:20:56)

quote:

ORIGINAL: mrstwinkle

I'd read several guides suggesting unlike other varnishes, polyurethane is difficult/near iimpossible to penetrate with chemicals.

Experience to the contrary would be interesting?

You are correct. Do you know how to use a scraper? With a sharp scraper you could have the finish off that back in short order.



Escribano -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 17:30:01)

quote:

With a sharp scraper you could have the finish off that back in short order.


Indeed, a cabinet scraper needs careful sharpening like a plane or chisel.



pundi64 -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 19:16:21)

Good luck.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 21:00:01)

Not a clue....

The stuff seems to bubble up then stick back down, so a 3 inch wide scraper is simply too big to tackle something with a very small target area . Had a go at it tonight with the short edge of an old credit card. Not great, but saves me getting crud stuck under my nails.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 21:02:00)

I have a kitchen knife sharpener. Run it through that?



Leñador -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 21:50:52)

quote:

I have a kitchen knife sharpener. Run it through that?

The credit card???

You're killing yourself, get a proper scraper and some Jasco. Like Estebanana said, if you let it soak in a bit it will be easier. I did this to a friends cheap Cordoba and it came out fine. We let it sit for a couple hours and when we came back it scraped off in 1/2 hour. He had some detail work after that but it was basically done.



Flamingrae -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 23:12:39)

quote:

a 3 inch wide scraper is simply too big to tackle something with a very small target area

You could try turning the scraper and using the shorter side. Alternatively, get a small piece of steel and sharpen up. I've used old kitchen knife blades to scrape too. Like has been said, sharpen the scraper on a stone then turn the edge back to make the burr with a round steel rod. If in doubt look up on line. Save the nails for playing please. Another option - get a scraper with a handle - more force.



jshelton5040 -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 22 2018 23:30:52)

quote:

ORIGINAL: Flamingrae

quote:

a 3 inch wide scraper is simply too big to tackle something with a very small target area

You could try turning the scraper and using the shorter side. Alternatively, get a small piece of steel and sharpen up. I've used old kitchen knife blades to scrape too. Like has been said, sharpen the scraper on a stone then turn the edge back to make the burr with a round steel rod. If in doubt look up on line. Save the nails for playing please. Another option - get a scraper with a handle - more force.

Get real! If he has never used a scraper it's hopeless to try to instruct him how to sharpen and use one. It's an acquired skill that takes some time and investment in tools to master.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 23 2018 10:56:51)

Have ordered some stripper called Paint Panther and a 43 mm palm scraper. Will compare and contrast methods....

https://www.toolstation.com/shop/p15403?searchstr=paint%20panther

https://www.toolstation.com/shop/p43813?table=no



Flamingrae -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 23 2018 23:56:03)

quote:

Have ordered some stripper called Paint Panther and a 43 mm palm scraper. Will compare and contrast methods....

Good for you - let us all know how you get on.



estebanana -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 24 2018 1:00:39)

I can put up a tutorial for scraping varnish. It's not difficult to prepare a scraper for paint removal. It does as Flamengrae said take some time to really learn how to make a scraper peel off wood in an expert way.

The poly finishes are not all the same. Some will dissolve rather well with stripper, just depends on which kind.

The thing I mentioned about covering the stripper to keep it wet for several hours is important. Poly will dissolve or soften, but you have to let a strong paint remover sit on it wet.

I know some tricks because I worked in two antique shops and a boatyard. I feel about 400 years old sometimes and being a complete know it all is very taxing on my humility.

If you want I'll show you the cowboy way of making the deadliest paint scraper.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 24 2018 11:20:40)

Paint scraper for cowboys. Interested, in case the one I'm picking up tonight proves to be useless.

Is the chemical stripper harmful to wood? As I've cleared an area (double size of original pic) already with the haridryer, I'm curious if any liquid runoff from the surface sitting there for a couple of hours is likely to cause serious damage.

Is leaving overnight to soak 'better' than leaving for a couple of hours. Or TOO caustic?



estebanana -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 24 2018 13:09:21)

Take a scraper and file or grind a radius on it, shallow arc.
Lay a fine metal file on the bench. Run the edge of the scraper on the file and make a sharp corner on the edge, along the arc.

There are a few if not several ways to get an edge on a scraper. This way makes a rough sharp corner, and it's adequate for the task. To put a fine turned edge of a scraper is a little more difficult and a waste of effort for a varnish removal job. The sharp corner on the arc will make the cutting area narrow, but it will have less hang up and cut into the finish. The swath will be narrow, but what is lacks in a wide cut it will make up for in cutting fast. Use some type of fanning motion to use the scraper, dig in a little.



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estebanana -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 24 2018 13:20:06)

Drag the scraper edge on the file. Make a hard edge.

There are ways to sharpen scrapers for making shavings practically peel off soft woods, but this method suffices for paint off work.



Images are resized automatically to a maximum width of 800px



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 24 2018 16:18:46)

Thanks. Isn't there a danger of gouging out the wood using an arced/curved surface rather than perfectly straight edge?



estebanana -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 24 2018 22:20:26)

You go lightly until you learn the amount of pressure you need to scrape the film off. The smaller contact surface allows you to cut. A wide swath will cut more shallow and be frustrating. You develop speed and a light surface sweeping fan motion as you scrape and it can go pretty fast. Once you get an uneven surface and there are dips and hollows, then a flat scraper passed over that will level off more film. It's a process, not a pleasure boat.

The raw wood area, tape it off so you don't get remover on there. Then test the remover on another spot.



Echi -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 25 2018 7:47:10)

This is a valuable info. Scraper is the best way.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 27 2018 11:14:47)

Chemicals and scraper. Bit of a trainwreck. The stuff dries up quite quickly and goes into hard sticky lumps making it difficult to judge what is going on. Simply struggled to get purchase for scraper, and ended up with very uneven result and a couple of horrible gouges where what I assume is the laminate top layer peeling off. Yeah, my scraping skills suck. 20/20 hindsight I should just have wiped it off and written chemicals off as a bad choice.

Feeling a bit dejected about the whole thing today, although did have another go with hairdryer over it and to be fair the chemicals have made the varnish a little easier to melt. Downside is it is also very uneven so hard to get a clean edge to scrape against now.

Ugh.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 28 2018 10:23:53)

With a bit of trial and error found method that seems to work. Apply chemicals, wait at most 10 mins, then try to skim top layer off. NOT get under it or attack from side, just skim the top off. The do another layer. Repeatedly. Top is almost done. Back is still a hideous trainwreck from the first round of attempts. Sides still to do. Pics would be attached but seems to e erroring for some reason on upload screen



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 28 2018 15:39:51)

Pics this morning



estebanana -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 28 2018 23:12:10)

I'm sorry you're having trouble. There's obviously learning curve.

OK, if you review what I wrote about using stripper, you need to cover it and make it air tight by applying to a small section and then taping foil or heavy plastic over the area to keep it wet. The older stripper mixtures form 20 30 years ago stayed wet longer and were more powerful, you put it on waited ten minutes and zipped the crap off with a putty knife. Now the stripper is less powerful so you have to coax it to stay wet and active longer.

Try my way of covering the stripper a leave it for 15-20 minutes. Make sure you use a low tack tape. Be mindful you don't pull out grain when you take the tape off. Or figure out some other way to cover the stripper. Put it on thick and slap foil over it.



Flamingrae -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 31 2018 1:43:44)

Ok, deep breathe.........you've started so you will need to finish. Make sure scraper is sharp. Hope you saved any bits that came out - you can patch back and fill any cracks. There is progress but try not to beat yourself up. Front is looking ok and with diligent work around the bridge and easy does it round the rosette, you should be fine. Light sanding with 400 grit or finer to finish. You need to strike a method for the back. Be better to get that nailed before going to the sides. Keep at it - everything passes.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 31 2018 15:11:08)

Few nights off mutilating the wood as I had to practice my farrucas to avoid wasting a guitar lesson.

Another go at it tonght - think my scraping technique of goop-scrape-goop-scrape in thin layers is working okay and have done most of sides too.

Front looks a bit uneven in colour with traces of the old red stain. In some ways it adds 'character', in some ways it looks crap. Rosette is a bit tricky, as is round the bridge. White spirit?

I'm a bit confused what the back is made of. It is a 1982 E model (student?) but it -looks- like real wood in that you can see what seems to be palo santo texture on inside. But the bits that have flaked from the back have a texture going the other way in below and much plainer. And the join down the middle comes right through to inside. Not a big issue either way, just bugging me as I don't know for sure.

I havn't touched the neck and head yet. The poly finish is quite nice to play in left hand but having orange up there would look peculiar. Might string it up this weekend anyway to see if the responsiveness has improved as much as I'd hoped.

Then decide finish. Rattle-can nitrocellulose, french polish (unlikely) or Danish oil.



Escribano -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 31 2018 16:13:06)

quote:

Then decide finish. Rattle-can nitrocellulose, french polish (unlikely) or Danish oil.


Try some Tru-Oil. Takes some time, but I like the finish. You can stain before applying, to even things out.



mrstwinkle -> RE: Hairdryer vs polyurenthane - day 1 (Jan. 31 2018 18:23:23)

Not seen tru-oil in the flesh that I know of. is it glossy / satin / matte?

With a lot of these finishes people seems to talk about the need for some kind of finishing layer (overcoat) or filler compound (surface leveller/undercoat). Or good as-is?



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