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Pre catalyzed laquer

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Forum topic by Woodson59 posted 05-09-2021 07:35 AM 477 views 1 time favorited 15 replies Add to Favorites Watch
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Woodson59

61 posts in 2253 days


05-09-2021 07:35 AM

Alright, I got talked into shellac then pre-catalyzed lacquer as best finish for chatoyance and longevity. First shot out of my gun went great everything after was a nightmare, until I watched some you tube videos to dilute more and add retarder and get smaller needle, but it still fells like a crap shoot as to the finish I get. So I sand it down to 400 each time and wipe with naphtha. Funny thing this stuff (Mohawk pre-cat clear semi is workable with no cut on a freshly opened can and needs more cut and retarder every try there after. Will it have time to lay down or dimple like a golf ball or dry before it hits the surface and leave sandy streaks? Who knows. I’m assuming there’s a way to measure viscosity and not go off volumetric cuts. How do I get consistency and not just pray coat 9 will be it


15 replies so far

View Fred Hargis's profile

Fred Hargis

7028 posts in 3616 days


#1 posted 05-09-2021 10:33 AM

You need a #4 Ford cup to measure viscosity (search for how to use it). The one I linked (which can probably be had for less somewhere) would be fine. Other than that I’ve got nothing.

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

View CWWoodworking's profile

CWWoodworking

1903 posts in 1302 days


#2 posted 05-09-2021 11:56 AM

Be careful spraying too many coats. Precat has a mil limit. If you get too thick, there’s a chance of crazing.

Are you shooting both products from same gun?

Have you tried just precat?

View CaptainKlutz's profile

CaptainKlutz

4565 posts in 2617 days


#3 posted 05-09-2021 12:52 PM

How to more consistent?

1) Keep a log book on your spraying.
Record temperature, humidity, finish type, solvents used, how much solvent, tip size, and air pressures. etc.
With time and experience, can use log book to know best setting for current conditions on next spray session.

2) Check your equipment settings.
Golf ball like dimples is also called orange peel. Orange peel is often result of poor atomization, which is a usually a gun setup issue. If solvent is evaporating too fast with large pattern, you get dry spray on edges of pattern. Dry spray coupled with poor atomization, and laying down a heavy film to compensate is #1 cause of orange peel IME.
Here in dry sunny Arizona, it is nearly impossible to 100% stop orange peel in summer time, unless I spray early morning, before sun comes up.

3) Ambient weather conditions and project surface temperature have huge impact on solvent evaporation rates. Easiest way to get more consistent results is to use slower solvent blend, or more retarder than one might use based on weather. While this lowers the solids loading, requires more coats, and requires more patience for dry time between coats; the reward is usually a better flow out.
Also, Lacquer solvents tend to be fast evaporating. Be sure your spray booth does not have excess air flow blowing across the project. Even a small breeze, can change evaporation rate; and the quality of finish.

4) Learn more about solvents used for spraying finishes.
Not all lacquer thinner is same, unless you make mistake and use crap BORG lacquer thinner.
Automotive paint suppliers carry different blends of lacquer thinner intended for different temperature ranges.
In warm weather, you want a slower evaporation blend. In hot weather, you want slowest evaporation blend.
This PDF table is one of my favorite solvent references to help understand if a local brand lacquer thinner is fast, med, or slow evaporating blend.

Beyond using proper temperature lacquer thinner, choice of retarder is important. MAK is common mid-range retarder for lacquer. When you want ultimate in slow evaporation, Butyl cellosolve is retarder of choice for lacquer. Sherwin Williams offers retarder ‘K27’, which is blend of MAK/Butyl cellosolve and other solvents that works well for lacquer. I use a lot of Butyl cellosolve due AZ weather. It is one of the few retarders compatible with water based finishes and lacquer. I use MAK/PGMEA for retarding polyurethane and enamels.

Profile shows New Orleans, LA location? High humidity causes blush in lacquer. Mohwak sells No-blush retarder for humid spraying. The trapped moisture (or white blush) is typically removed with addition of PGMEA and slow evaporation Isopropyl alcohol to pull water to surface and let it evaporate from film.

Since lacquer dissolves existing lacquer film, can often spray straight no-blush retarder on surface to remove blush. Occasionally, can also spray lacquer thinner & retarder blend to help fix dry spray area too.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, Doom, despair, agony on me… - Albert King - Born Under a Bad Sign released 1967

View splintergroup's profile

splintergroup

5306 posts in 2345 days


#4 posted 05-09-2021 02:13 PM

I shoot Mohawk pre-cat all the time. When I first tried it (with my HVLP turbine), I got a lot of orange peel. It was hot that day and the heat from the turbine didn’t help so I went with a compressor supplied “touch-up” gun and thinned the mix about 10% with Mohawk retarder. Flowed out perfectly.

Check your viscosity (Ford cup), chances are you’ll need to reduce it (even though it states the mix is ready to spray). Don’t use too high of pressure and of course don’t lay too thick.

Tip #1, spray a test surface (I use a sheet of masking paper on the wall). You need to adjust your gun to get a correct pattern and flow before hitting your project.

View Rich's profile

Rich

6939 posts in 1712 days


#5 posted 05-09-2021 02:23 PM

Those pieces are beautiful. You’re obviously a skilled craftsman. What confuses me is that you used the same finish on your toy box project (well-deserved DT3) and it’s gorgeous. Why do you suppose this one is not faring as well?

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View JackDuren's profile

JackDuren

1601 posts in 2083 days


#6 posted 05-09-2021 02:55 PM

I spray S&W pre-cat T 77 right out of a harbor freight spray gun. Not that hard…

View AlaskaGuy's profile

AlaskaGuy

6639 posts in 3432 days


#7 posted 05-10-2021 02:11 AM



I spray S&W pre-cat T 77 right out of a harbor freight spray gun. Not that hard…

- JackDuren


I guess that clears up all the OP’s questions.

-- Alaskan's for Global warming!

View CWWoodworking's profile

CWWoodworking

1903 posts in 1302 days


#8 posted 05-10-2021 02:44 AM

I reread your post and have a few suggestions.

1. Try spraying without shellac. I don’t think this is it, but it will rule it out.

2. Don’t wipe with naphtha. I never wipe with anything. Never a problem with dust. Again this may not be it, but easy to single out.

3. Type of sand paper? This is long shot but some papers have adverse effects on finishes.

Golf ball dimples to me suggest contamination. Think outside the box for anything that it could be. If it is orange peel, add some slow thinner and possibly retardant.

I use chemcraft and have used SW precat in the past. I thin it 10-15% with lacquer thinner. Sprays like a dream.

Your pictures look good. I don’t see anything?

View Rich's profile

Rich

6939 posts in 1712 days


#9 posted 05-10-2021 04:00 AM


I guess that clears up all the OP s questions.

- AlaskaGuy

+1, AG. You took the words right out of my mouth.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View Woodson59's profile

Woodson59

61 posts in 2253 days


#10 posted 05-10-2021 04:49 AM


Those pieces are beautiful. You re obviously a skilled craftsman. What confuses me is that you used the same finish on your toy box project (well-deserved DT3) and it s gorgeous. Why do you suppose this one is not faring as well?

- Rich

I was assuming it was all a viscosity issue. I hadn’t really taken into account humidity and ambient temp. But I’m also thinking I need a even smaller needle on my turbine gun. My biggest issues have been orange peel. I had a compressor gun previously I could dial in better.

The only coat that has to lay perfectly is the final one. I hit the combo often enough, but I think I need a Ford cup and to monitor humidity and adjust accordingly. I hadn’t thought about my shop temp and humidity. It’s air conditioned and dehumidified, but I exhaust fan it while spraying and it always ends up on par with the outdoors thereafter

View Rich's profile

Rich

6939 posts in 1712 days


#11 posted 05-10-2021 05:16 AM


I was assuming it was all a viscosity issue. I hadn’t really taken into account humidity. But I’m also thinking I need a even smaller needle on my turbine gun. My biggest issues have been orange peel. I had a compressor gun previously I could dial in better.

The only coat that has to lay perfectly is the final one. I hit the combo often enough, but I think I need a Ford cup and to monitor humidity and adjust accordingly. I hadn’t thought about my shop temp and humidity. It’s air conditioned and dehumidified, but I exhaust fan it while spraying and it always ends up on par with the outdoors thereafter

- Woodson59

I’ll start by saying I live in the arid desert southwest and have no experience at all spraying lacquer in an environment like New Orleans (but I do love visiting and dining there).

However, consider that while a smaller needle will give you a finer mist, and for many finishes that might translate to a finer finish, but with lacquer it means that the finish is more finely aerosolized and more prone to start to dry before it hits the surface.

I actually use a 1.8mm needle in mine for larger pieces. It produces a wet coat that, with a retarder, flows out and gives me a smooth finish. On a box like yours I would also position the surface I’m spraying so it’s flat and the lacquer is less likely to sag. I go with roughly a 10% cut with the retarder, but in your climate you might need more. Do lots of test boards to find the best ratio for you. It might even vary seasonally.

I believe you’re about 90% of the way there and just need to fine-tune your application. Again, that’s beautiful work you do.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View Woodson59's profile

Woodson59

61 posts in 2253 days


#12 posted 05-10-2021 10:56 PM


I was assuming it was all a viscosity issue. I hadn’t really taken into account humidity. But I’m also thinking I need a even smaller needle on my turbine gun. My biggest issues have been orange peel. I had a compressor gun previously I could dial in better.

The only coat that has to lay perfectly is the final one. I hit the combo often enough, but I think I need a Ford cup and to monitor humidity and adjust accordingly. I hadn’t thought about my shop temp and humidity. It’s air conditioned and dehumidified, but I exhaust fan it while spraying and it always ends up on par with the outdoors thereafter

- Woodson59

I ll start by saying I live in the arid desert southwest and have no experience at all spraying lacquer in an environment like New Orleans (but I do love visiting and dining there).

However, consider that while a smaller needle will give you a finer mist, and for many finishes that might translate to a finer finish, but with lacquer it means that the finish is more finely aerosolized and more prone to start to dry before it hits the surface.

I actually use a 1.8mm needle in mine for larger pieces. It produces a wet coat that, with a retarder, flows out and gives me a smooth finish. On a box like yours I would also position the surface I m spraying so it s flat and the lacquer is less likely to sag. I go with roughly a 10% cut with the retarder, but in your climate you might need more. Do lots of test boards to find the best ratio for you. It might even vary seasonally.

I believe you re about 90% of the way there and just need to fine-tune your application. Again, that s beautiful work you do.

- Rich

Thanks, finishing has always been the bane of completing a project for me. I do a test board. It generally behaves better then the piece itself, but I’m not hitting multiple faces on the test and having over spray.either. I believe more retarder may be the key. But after returning leftovers to the can repeatedly I keep thinking it has some residual and I can go a hair lighter. But i may need to look at tables and dose accordingly for ambient temps.

Thanks again

View Woodson59's profile

Woodson59

61 posts in 2253 days


#13 posted 05-10-2021 11:00 PM



How to more consistent?

1) Keep a log book on your spraying.
Record temperature, humidity, finish type, solvents used, how much solvent, tip size, and air pressures. etc.
With time and experience, can use log book to know best setting for current conditions on next spray session.

2) Check your equipment settings.
Golf ball like dimples is also called orange peel. Orange peel is often result of poor atomization, which is a usually a gun setup issue. If solvent is evaporating too fast with large pattern, you get dry spray on edges of pattern. Dry spray coupled with poor atomization, and laying down a heavy film to compensate is #1 cause of orange peel IME.
Here in dry sunny Arizona, it is nearly impossible to 100% stop orange peel in summer time, unless I spray early morning, before sun comes up.

3) Ambient weather conditions and project surface temperature have huge impact on solvent evaporation rates. Easiest way to get more consistent results is to use slower solvent blend, or more retarder than one might use based on weather. While this lowers the solids loading, requires more coats, and requires more patience for dry time between coats; the reward is usually a better flow out.
Also, Lacquer solvents tend to be fast evaporating. Be sure your spray booth does not have excess air flow blowing across the project. Even a small breeze, can change evaporation rate; and the quality of finish.

4) Learn more about solvents used for spraying finishes.
Not all lacquer thinner is same, unless you make mistake and use crap BORG lacquer thinner.
Automotive paint suppliers carry different blends of lacquer thinner intended for different temperature ranges.
In warm weather, you want a slower evaporation blend. In hot weather, you want slowest evaporation blend.
This PDF table is one of my favorite solvent references to help understand if a local brand lacquer thinner is fast, med, or slow evaporating blend.

Beyond using proper temperature lacquer thinner, choice of retarder is important. MAK is common mid-range retarder for lacquer. When you want ultimate in slow evaporation, Butyl cellosolve is retarder of choice for lacquer. Sherwin Williams offers retarder K27 , which is blend of MAK/Butyl cellosolve and other solvents that works well for lacquer. I use a lot of Butyl cellosolve due AZ weather. It is one of the few retarders compatible with water based finishes and lacquer. I use MAK/PGMEA for retarding polyurethane and enamels.

Profile shows New Orleans, LA location? High humidity causes blush in lacquer. Mohwak sells No-blush retarder for humid spraying. The trapped moisture (or white blush) is typically removed with addition of PGMEA and slow evaporation Isopropyl alcohol to pull water to surface and let it evaporate from film.

Since lacquer dissolves existing lacquer film, can often spray straight no-blush retarder on surface to remove blush. Occasionally, can also spray lacquer thinner & retarder blend to help fix dry spray area too.

Best Luck.

- CaptainKlutz

Thanks for the technical side, written like my uncle the engineer who got me into this. I shall have to do research and pay more attention to ambient temps and humidity

View Woodson59's profile

Woodson59

61 posts in 2253 days


#14 posted 05-12-2021 06:00 AM



I spray S&W pre-cat T 77 right out of a harbor freight spray gun. Not that hard…

- JackDuren

Jack,
I use wedges in dovetails, sawdust and super glue in cracks and rub out most finishes.

I wish I hit it perfectly every time, that’s a really nice piece. Not sure your geography to have such great consistency, Sometimes I may get close to perfection and others I’m confused, but every time I get closer, but these guys are a wealth of knowledge. If it sounds good I look at their project pictures and say this guy has something to add or whisper quietly that guy heard that at a workshop at Home Depot. But when I ask questions about rather specific not used by lay people finishes. There’s generally a whole lot of knowledge I didn’t consider. Someone on this blog suggested shellac first which has added chatoyancy and taken away the blushing and blotchiness from cherry also made for way more consistent gel stain, I’ll be asking stupid questions about dyes next time. But asking questions has led to my last two projects hitting daily top 3,

This is one of my favorite projects so I have to repeat or better and that requires an awesome finish. Thanks guys

View JackDuren's profile

JackDuren

1601 posts in 2083 days


#15 posted 05-12-2021 01:35 PM

I’m afraid I don’t get into all the crazy formulas others come up with. I’m pretty straight forward. These pieces do have two finishes , pre-cat where not touched and polyurethane where there are. Some finishes are harder and cannot be touched up as easily and others are.

Nice work. Stepping out of the box like you’ve done moves you up the ladder as woodworker. Many get stuck and can’t move forward. Playing it safe will keep you from landing furniture jobs…

I got forced into retirement, so I only occasionally dabble in woodworking.now..

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