Re-amalgamation of Lacquer - Woodworking Talk - Woodworkers Forum
 
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post #1 of 12 Old 03-25-2012, 05:19 PM Thread Starter
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Re-amalgamation of Lacquer

I recently finished a table with pre-cat NC lacquer. It turned out beautiful until we placed a centerpiece on it and overnight noticed that it had marred the lacquer. (I should have known better that 5 days of drying was not enough)

Do I need to take it apart, haul it back out to the shop and re-shoot the whole top, or can I just re-amalgamate the spots? (i.e. will a "spot" treatment show an inconsistent sheen with the rest of the table)

I was thinking of re-spraying the area with a 50/50 mix of lacquer thinner and retarder.

Has anyone had any experience doing this?
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post #2 of 12 Old 03-25-2012, 05:37 PM
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Quote:
Originally Posted by ourwhitehouse View Post
I recently finished a table with pre-cat NC lacquer. It turned out beautiful until we placed a centerpiece on it and overnight noticed that it had marred the lacquer. (I should have known better that 5 days of drying was not enough)

Do I need to take it apart, haul it back out to the shop and re-shoot the whole top, or can I just re-amalgamate the spots? (i.e. will a "spot" treatment show an inconsistent sheen with the rest of the table)

I was thinking of re-spraying the area with a 50/50 mix of lacquer thinner and retarder.

Has anyone had any experience doing this?
If by "marred" you mean indentations then no it wont likely work, if you mean something else then it would have to be seen, post pics please. Even then it's doubtful in the sense of not showing at all. Pics would help make the decision for sure but i would be fairly certain you'd still need to bite the bullet and recoat if you still have room for extra mil thickness. You must have really piled it on there to not be dry in 5 days or used alot of retarder to begin with, has your weather been bad/humid/rainy?

Oh No.... tell me this is not your bubinga table!! Why, if so, did you use pre cat instead of regular nitrocellulose like you had outlined in your finishing schedule originally??

Last edited by chemmy; 03-25-2012 at 06:11 PM.
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post #3 of 12 Old 03-26-2012, 12:23 PM Thread Starter
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Yes, it is my bubinga table. Thanks to some of your previous suggestions, it turned out beautiful, until...

I did use a fair amount of retarder to deal with sheen uniformity from overspray and humidity both.

At this point, I don't think I have anything to lose other than to try it out. If it doesn't work, I just have to haul it back into the shop.
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post #4 of 12 Old 03-26-2012, 12:41 PM
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The defect isn't obvious in the pictures.






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post #5 of 12 Old 03-26-2012, 04:13 PM
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Did you make a sample to go along with it as you finished? If so, and hopefully you did, then test it out on the sample first ok?

I'm concerned that with a lot of retarder you may find that if you spray another coat of 50/50 in hopes to blend it out, especially a wet coat, it could react. Again I'm concerned if it doesn't work and you then try to scuff sand and re-coat it could even be worse and crinkle from the new coating or laying open the new sanding marks or both or other. Plus as i stated since you used pre-cat instead of regular NC lacquer, you have to take into consideration your mil thickness as of now. Applying heavy or thick coats especially when heavily retarded, could easily down the road cause premature cracking and such. normally pre cats are not supposed to exceed 4 mils [ 4 thousandths] when dry, that's thinner than a business card, and that includes not just the pre-cat but any other sanding sealers or other beneath the pre-cat. but it's to late to change it now. Boy....next time you have an issue with weather/humidity, don't add the retarder to the finish, instead just spray it with the 50/50 R/T in mist coats to clear up any blushing after the UN-retarded coat is applied ok?

Sorry i can't be of more help as things stand, hope you don't end up having to strip it.

PS: If by chance the retarder does not fix the damage, please wait about a month or so before trying to re-coat ok or even longer if possible, once the finish is hard, then it will be much safer to try and sand and re-coat. But even then thier are no guarantees, especially as i said if the mil thickness has already been reached or exceeded.

Last edited by chemmy; 03-26-2012 at 04:17 PM.
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post #6 of 12 Old 03-26-2012, 05:25 PM
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novice finishing question

Is the issue an indentation or a discoloration? Why couldn't you wait until it's totally cured/hard and then just watersand and buff it out if it's an indentation? A discoloration would be more difficult I would imagine.....
Another option might be a local mask of tape or putty and flood the area with solvent by using an injector syringe or a spray gun or bottle.
I'm just throwing out ideas and asking questions and not proposing solutions. Someone may have tried a similar "fix" who can comment?

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 03-26-2012 at 07:25 PM.
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post #7 of 12 Old 03-26-2012, 06:32 PM
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Without a better picture of the actual damage I wouldn't venture offering a specific fix. Maybe others see something I don't. In the mean time, ask whatever you think may be pertinent to your work.








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post #8 of 12 Old 03-26-2012, 08:28 PM
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What am I missing or not understanding here? I have never had any dealings with lacquer where it was not totally cured well within 5 days.

George
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post #9 of 12 Old 03-26-2012, 11:04 PM
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What am I missing or not understanding here? I have never had any dealings with lacquer where it was not totally cured well within 5 days.

George
sorry George, your missing the part where he added 20% retarder to his lacquer in multiple heavy coats to avoid blushing problems he was having causing a lot of slow evaporative solvent entrapment in the finish. That's like 4 times as much as should have been used. usually 1 oz. per qt. is standard, but i don't put any in mine even if it's full saturation dew point. Normally like in your case evidently, with no retarder you can put a table top into service in 5 days with caution to the client about heavy objects, etc.. but this was not the case.
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post #10 of 12 Old 03-27-2012, 05:10 PM Thread Starter
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I didn't run a test board in parallel. It's a great idea. I'm going to have to make that a standard practice in the future.

I don't think I'm near 4 mils of coating.

Since it's pre-cat NC I wondered about the ability to re-amalgamate the top once the chemical "reaction" has taken place. So I decided to call the manufacturer of the NC. To my surprise, their pre-cat has no time limit under which you can re-melt the finish (Unlike others such as Sherwin Williams that say 5 days) As such, they recommended a light sanding of the blemishes followed by spraying 10 oz thinner/2 oz retarder (or better 1:1 thinner and butyl acetate for more open time, but I can't find that in anything less than a gallon at $40+).
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post #11 of 12 Old 03-27-2012, 05:40 PM
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Quote:
Originally Posted by ourwhitehouse View Post
I didn't run a test board in parallel. It's a great idea. I'm going to have to make that a standard practice in the future.

I don't think I'm near 4 mils of coating.

Since it's pre-cat NC I wondered about the ability to re-amalgamate the top once the chemical "reaction" has taken place. So I decided to call the manufacturer of the NC. To my surprise, their pre-cat has no time limit under which you can re-melt the finish (Unlike others such as Sherwin Williams that say 5 days) As such, they recommended a light sanding of the blemishes followed by spraying 10 oz thinner/2 oz retarder (or better 1:1 thinner and butyl acetate for more open time, but I can't find that in anything less than a gallon at $40+).
If you have a real paint store or auto body and paint retailer in your area, you should be able to get retarder in quarts. If not maybe a "slow lacquer thinner".

I still haven't seen the exact damage, but the fix may depend on how bad there is indentions, and whether a light sanding would be necessary. You may have to add some spot lacquer to the area (depending on the area), to then shoot the mix to get a flow out. You could create a visibly "fixed" area. If that's the case, you may have to re-shoot a light coat on the entire top to get an overall even sheen.




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post #12 of 12 Old 03-27-2012, 08:42 PM
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Quote:
Originally Posted by ourwhitehouse View Post
I didn't run a test board in parallel. It's a great idea. I'm going to have to make that a standard practice in the future.

I don't think I'm near 4 mils of coating.

Since it's pre-cat NC I wondered about the ability to re-amalgamate the top once the chemical "reaction" has taken place. So I decided to call the manufacturer of the NC. To my surprise, their pre-cat has no time limit under which you can re-melt the finish (Unlike others such as Sherwin Williams that say 5 days) As such, they recommended a light sanding of the blemishes followed by spraying 10 oz thinner/2 oz retarder (or better 1:1 thinner and butyl acetate for more open time, but I can't find that in anything less than a gallon at $40+).
In the future, along with your new standard practice of running a sample [or more] along with the project, please purchase a good but cheap wet mil guage so you can keep track of how many mils per coat your applying, that way there will be no guesswork ok? less than 5.00 for a decent wet mil guage. I was going by what you had posted as your schedule on homestead as to trying to determine the mils, but since we all spray differently i can't say or know. With a wet mil guage ---- you will know.
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