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Only use gloss finish. Myth?

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Forum topic by Carloz posted 07-19-2017 06:38 PM 1099 views 0 times favorited 26 replies Add to Favorites Watch
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Carloz

963 posts in 426 days


07-19-2017 06:38 PM

I read it all the time here and in other places. ”Do not use anything but the gloss finish for all your base/intermediate coats and only use the desired finish as the top coat”. The reasoning behind this that the additives ( some micro balls ) manufacturers use to achieve duller finish are going to contaminate the finish and make is less transparent.

I do not have anything to back it up with but naively I would guess that the manufacturers would use the additives with the same optical properties as the main finish. As such they should not change the transparency of the finish. You cannot see glass in water for example.
As I mistaken or the whole story is an urban legend ?


26 replies so far

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splintergroup

1694 posts in 1057 days


#1 posted 07-19-2017 07:25 PM

Polyurethane uses added siilca sand to achieve the “low gloss” and “satin” sheens. The added silica reflects some of the light. If you build up many coats with this mix, the added layers begin to obscure the wood, think of it as a cloudy finish.

By using only the “clear” finishes as undercoats, the transparency is not diminished.

Does it really matter?

I can see the difference on some woods with lots of coats, but I have to be looking for it. In my opinion, unless the finish layers are really thick, no need to worry.

View Fred Hargis's profile

Fred Hargis

4756 posts in 2328 days


#2 posted 07-19-2017 07:41 PM

I only use gloss, even when I wind up with the satin or semi (or whatever) I’ll use them without stirring to leave the silica on the bottom of the can. I’ve been told by someone who is knowledgeable on such things that the sheen will get even flatter over time with those that have the flattening agents. The explanation is that as the finish cures, it will shrink very slightly. As this shrinkage occurs, the surface gets more rough (reducing sheen) due to the silica. So I use gloss, and if I want it less shiny I work it down with an abrasive (from pumice to a brown paper bag) to get the appearance I want.

-- Our village hasn't lost it's idiot, he was elected to congress.

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OSU55

1423 posts in 1824 days


#3 posted 07-21-2017 03:32 PM

I agree with splinter. My own testing showed that with several thick coats, and having pieces side by side for comparison, I could see some very slight difference. None of the 1/2 dozen observers said there was any difference, until I told them they were different. 2 said yes, I see a little, 4 said they still look the same. So, I dont worry about it unless I do a really thick film finish, which rarely happens.

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Carloz

963 posts in 426 days


#4 posted 07-21-2017 04:38 PM

That is really helpful to know, thanks !


I agree with splinter. My own testing showed that with several thick coats, and having pieces side by side for comparison, I could see some very slight difference. None of the 1/2 dozen observers said there was any difference, until I told them they were different. 2 said yes, I see a little, 4 said they still look the same. So, I dont worry about it unless I do a really thick film finish, which rarely happens.

- OSU55


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Rick_M

10610 posts in 2215 days


#5 posted 07-21-2017 05:46 PM

It’s about convenience, you can achieve any finish from gloss to flat from a single can.

-- http://thewoodknack.blogspot.com/

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Rich

1976 posts in 424 days


#6 posted 07-21-2017 06:19 PM


It s about convenience, you can achieve any finish from gloss to flat from a single can.

- Rick M

Just because you can doesn’t mean that you should. Manufacturers formulate their products to a particular sheen, so let’s say you take a can of satin topcoat with a sheen of 35 to 45 and use or pour 25 or 30 percent of it off the top without stirring. Now, when you stir that product you have something closer to flat or dead flat, or anywhere in between. You just don’t know. Maybe you’re fine with that, but I put too much work into my projects to just wing it on the finish.

As to the original subject of the thread, I’ve found what Splinter and OSU55 said to be true for me as well, so I don’t sweat it.

-- No matter how much you push the envelope, it'll still be stationery.

View DrDirt's profile

DrDirt

4413 posts in 3577 days


#7 posted 07-21-2017 07:21 PM

My thinking is along what Rich said.

I was taught to use gloss for all coats. Not e.g. Satin as the final coat.
This was about Repairability and repeatability in other pieces.
The ammount of ‘flattening agent will be different with every stirring, or one time you need to add Floetrol, or Blush control… so it is always a changing recipe.

So the recipe for a satin sheen was – hand sand wood with 320… coat with gloss, (de-nib with paper bag) 2 more coats. Then rub with 0000 steel wool (liberon) and then paste wax or briwax.

6 months later a repair, or a matching chair is needed. No problem to get an identical piece again the steel wool will blend a repair better than struggling with trying to get refelction to 75 vs 85. you set the sheen by hand, not chemistry.

gloss was same initially but then rub out with automotive rubbing compound if you wanted ‘grand piano gloss’

I a no master finisher, but that is how I was taught.

-- “The two most important days in your life are the day you are born and the day you find out why.” Mark Twain

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Carloz

963 posts in 426 days


#8 posted 07-21-2017 09:46 PM


So the recipe for a satin sheen was – hand sand wood with 320… coat with gloss, (de-nib with paper bag) 2 more coats. Then rub with 0000 steel wool (liberon) and then paste wax or briwax.
- DrDirt

Sure with the coat of wax the sheen can be very nice and not too glossy. However it has a big downside of being not durable, so we are talking about pure polyurethane finish here.

View Rich's profile

Rich

1976 posts in 424 days


#9 posted 07-21-2017 11:05 PM

So the recipe for a satin sheen was – hand sand wood with 320… coat with gloss, (de-nib with paper bag) 2 more coats. Then rub with 0000 steel wool (liberon) and then paste wax or briwax.
- DrDirt

Sure with the coat of wax the sheen can be very nice and not too glossy. However it has a big downside of being not durable, so we are talking about pure polyurethane finish here.

- Carloz

He said coat with gloss, de-nib and add two more coats. It’s not a wax-only finish he was talking about. That’s the way I was taught to do it too. The advantage is that the gloss topcoat can be any film — poly, shellac, etc — and the sheen is not dependent on the product, but on your technique. These days, unless I’m using oil, I just go with products like Mohawk pre-cat lacquer that have a range of sheens you can choose from.

-- No matter how much you push the envelope, it'll still be stationery.

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Rick_M

10610 posts in 2215 days


#10 posted 07-21-2017 11:58 PM


It s about convenience, you can achieve any finish from gloss to flat from a single can.

- Rick M

Just because you can doesn t mean that you should. Manufacturers formulate their products to a particular sheen, so let s say you take a can of satin topcoat with a sheen of 35 to 45 and use or pour 25 or 30 percent of it off the top without stirring. Now, when you stir that product you have something closer to flat or dead flat, or anywhere in between. You just don t know. Maybe you re fine with that, but I put too much work into my projects to just wing it on the finish.

As to the original subject of the thread, I ve found what Splinter and OSU55 said to be true for me as well, so I don t sweat it.

- RichTaylor

Your tone suggests disagreement but nothing you said contradicts me. Maybe you misread my post.

-- http://thewoodknack.blogspot.com/

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Rick_M

10610 posts in 2215 days


#11 posted 07-22-2017 12:05 AM



My thinking is along what Rich said.

I was taught to use gloss for all coats.

- DrDirt


Rick, not Rich. I’m the one who suggested gloss. Rich is the one who brought up satin.

Sure with the coat of wax the sheen can be very nice and not too glossy. However it has a big downside of being not durable, so we are talking about pure polyurethane finish here.

- Carloz

It isn’t the wax that gives you the satin finish, it’s sanding with 320 sandpaper. It scatters the light rays.

-- http://thewoodknack.blogspot.com/

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Rich

1976 posts in 424 days


#12 posted 07-22-2017 12:19 AM


Your tone suggests disagreement but nothing you said contradicts me. Maybe you misread my post.

- Rick M

Misread it? It was a single sentence…lol. On the contrary, I think you misread mine since I didn’t say you were wrong, I said it was a dumb idea. If you’re OK with random, unpredictable sheen on your project, that’s your business. I’m not.

-- No matter how much you push the envelope, it'll still be stationery.

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Rich

1976 posts in 424 days


#13 posted 07-22-2017 12:25 AM

Rick, not Rich. I m the one who suggested gloss. Rich is the one who brought up satin.

Goodness. A little touchy, are we? :) I was actually talking about sheen, as was DrDirt, but that seems to have gone over your head.

It isn t the wax that gives you the satin finish, it s sanding with 320 sandpaper. It scatters the light rays.

- Rick M

Again, you misread his post and missed the part about the 0000 steel wool. That, combined with the wax is what gives you the softer sheen. Sanding the wood to 320 before applying three coats of gloss won’t scatter anything.

-- No matter how much you push the envelope, it'll still be stationery.

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Rick_M

10610 posts in 2215 days


#14 posted 07-22-2017 12:50 AM

What is it that you think is a dumb idea exactly? It’s pretty clear that you misunderstood my post.

-- http://thewoodknack.blogspot.com/

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Rich

1976 posts in 424 days


#15 posted 07-22-2017 01:02 AM



What is it that you think is a dumb idea exactly? It s pretty clear that you misunderstood my post.

- Rick M

LOL. Let it go.

-- No matter how much you push the envelope, it'll still be stationery.

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