Newbie question about HVLP and varnish

[Tom Jones III]

I'm planning on taking down my front door this weekend and giving it another coat of "spar" varnish. Is this a good candidate for spraying with an HVLP sprayer?

This is a solid walnut entry door that I made and initially brushed on a few coats of Interlux Goldspar satin varnish. It has been about a year and I want to give it a fresh coat. I recently got one of the cheap Rockler HVLP sprayers for another project and I'm wondering if I should attempt varnish with it or would I be better off just brushing it on?

[Scott Holmes]

The choice is yours. I would use a brush. My reasons are as follows...

SPRAYING
Setting up and adjusting equipment = 20-40 minutes (don't forget the time needed to protect stuff from overspray)
Spraying door = 3 minutes
Material used = 1 to 2 quarts. (my system has a 50' hose)
Time to rinse and clean equipment = 45 mins
Total time = ~1 hour +


BRUSH
Setting up and adjusting equipment (BRUSH) = 1 minute
Finishing door = 20 minutes
Material used = < 1 quart (provided I don't spill any)
Time to rinse and clean equipment = 5 mins
Total time = ~30 minutes

Extra time saved = Priceless...

Your times will vary.

If I were going to be doing more than one door I'd be spraying

[Chris Fournier]

The best way to answer your question is with a question: why do you want to put another coat of finish on your one year old door?

If the finish on your door has not failed and is presently protecting the wood you will not gain anything by spraying on another coat. All finish manufacturers will spec a dry film build for their product and thicker is rarely better.

If you do indeed need to put another coat on your door a good HVLP sprayer will be a pleasure to use once you get the viscosity right. Again look to the manufacturer of your finish for details on the spray application of the product. Your door is pretty high stakes stuff so I'd be sure to practice until you know that you can lay it on real sweet!

Spraying won't hide any of the current finishing defects so careful prep work is required.

[Tom Jones III]

It sounds like Scott has sound thinking on the setup/teardown time. The only thing he did not account for is how much I despise putting on a finish.

Chris, the reason I'm putting on another coat is because I was under the impression that it has to be renewed every so often and that if I did it now it would be much easier than waiting until it "needed it". Also, I was wrong, it has been 2 years and it is an east facing door getting direct sunlight.

[Chris Fournier]

Sounds like your door gets a tough life but unless the current finish looks poorly I wouldn't recoat before you need to. I'd wait until I saw the finish looking a bit tired but not decrepit.

My experience would be that spraying would be much faster than brushing even with set up, masking and clean up. Brushing has the ultimate transfer efficiency of the two techniques but if you're using a quart or two as Scott suggests then you're doing something terribly wrong - unless it is a door on the scale of an aircraft hanger!

This past summer I made and finished two 36" X 92" ash doors for a customer and used about 1.5 quarts of varnish (thinned). This was for two raw wood doors, both sides and applied using my HVLP set up. There was about 4 square feet of glass that didn't need finishing.

I would avoid using a pressure pot with the required hoses unless you're shooting on-site millwork where there is a large volume to finish and ceiling work or other really awkward surfaces where the cup angle comes into play. Clean up shouldn't take more than 10 minutes with your set up once you get a good system down pat.

I'd take the time to cobble together a good set up to hold the door to allow you spray as you feel most comfortable. This is really key when it comes to spray finishing as a good set up lets you manipulate the gun more easily and manintain a consistent gun to surface distance.

[Scott Holmes]

Chris,

I don't own a HVLP so my 1-2 Qts is based on needing to get finish to the gun of my Air-Assisted Airless unit with a 50' hose. I would not use nearly that much finish on the project, but I need almost a quart to get the finish thru the hose to the gun. I don't use it for a small 1 door jobs.

I wish I could clean my system in 10 minutes, 20 minutes at best, and with varnish I'm extra careful during clean up. Shellac and lacquer clean up is faster.

[Chris Fournier]

Chris,

I don't own a HVLP so my 1-2 Qts is based on needing to get finish to the gun of my Air-Assisted Airless unit with a 50' hose. I would not use nearly that much finish on the project, but I need almost a quart to get the finish thru the hose to the gun. I don't use it for a small 1 door jobs.

I wish I could clean my system in 10 minutes, 20 minutes at best, and with varnish I'm extra careful during clean up. Shellac and lacquer clean up is faster.

Well that explains the estimates of "your" time to spray but the OP has an HVLP set up!

[Tony Bilello]

If you have a clear finish, such as varnish, and you are getting direct sunlight, yes you should do it every year. Varnish does not slowly degrade like other finishes. When it starts to go, it goes quickly. If you do it every year, your prep is no more than a washdown and a light sanding. Let it deteriorate and it is a major sanding job.
Ask anyone that owns a boat.

[Gary Max]

Your words---------------[I recently got one of the cheap Rockler HVLP ]
Use a brush-----you will have more control.
I own one of the Rockler systems and they can produce varying results.

[Tom Jones III]

That is exactly what I was thinking of ... growing up we had a sailboat in south Texas. Think of a furnace except with high humidity and salt water. I have strong childhood memories of taking off all the wooden parts every winter, sanding them down to bare wood and then putting on 6 coats of spar varnish.

If you have a clear finish, such as varnish, and you are getting direct sunlight, yes you should do it every year. Varnish does not slowly degrade like other finishes. When it starts to go, it goes quickly. If you do it every year, your prep is no more than a washdown and a light sanding. Let it deteriorate and it is a major sanding job.
Ask anyone that owns a boat.

[Chris Fournier]

I had a cedar canvas canoe like that. It certainly didn't need yearly attention but I never used it in the Lonestar State!

I think that you've pretty much answered a "prep" question though - down to the bare wood. Seems that putting good varnish over bad would be a real waste of time. Honestly I think that you're in the realm of "If it ain't broke don't fix it" territrory.

Nothing like a project to get your spray finishing skills up to snuff though.

[Howard Acheson]

Tom, the way to tell if you door needs to be refinished is to look at the finish carefully. Varnish begins to turn cloudy and more amber as it gets close to its time of failure. If you get to your rehabilliting without much delay you can easily refresh the look of the door. What is needed is a light but thorough sanding with 320 paper. The surface should be completely grayish when you are done. The idea is not to sand through the finish rather it's to remove the cloudy upper part of the varnish. Then apply two new coats and you should be done.

Us boaters know that brightwork on boats must be cared for annually in most areas of the country. But, the quick touchup I described above should keep the finsh looking good for 5-10 years. At some point it will need to be completely stripped and refinished.

Interlux is an excellent exterior varnish. But, I would not spray it unless you are an experianced sprayer. Oil based spar varnishes are slow drying and if you don't have a spray booth you will need to spray outdoors. The slow drying overspray will get on every thing in the area leaving a sort of crust on anything it settles on. Much better to brush.

[Tony Bilello]

Tom, the way to tell if you door needs to be refinished is to look at the finish carefully. Varnish begins to turn cloudy and more amber as it gets close to its time of failure. If you get to your rehabilliting without much delay you can easily refresh the look of the door. What is needed is a light but thorough sanding with 320 paper. The surface should be completely grayish when you are done. The idea is not to sand through the finish rather it's to remove the cloudy upper part of the varnish. Then apply two new coats and you should be done.

Us boaters know that brightwork on boats must be cared for annually in most areas of the country. But, the quick touchup I described above should keep the finsh looking good for 5-10 years. At some point it will need to be completely stripped and refinished.

Interlux is an excellent exterior varnish. But, I would not spray it unless you are an experianced sprayer. Oil based spar varnishes are slow drying and if you don't have a spray booth you will need to spray outdoors. The slow drying overspray will get on every thing in the area leaving a sort of crust on anything it settles on. Much better to brush.

+1 Howard is right on. I have a bad internet connection at this holiday location so I wasnt able to put it in such detail.
I think the most important part of his post is "The idea is not to sand through the finish rather it's to remove the cloudy upper part of the varnish".
The whole idea is to repair (freshen up) the finish before it entirely degrades.

[Tom Jones III]

Well that is the best news I've had all year! I'll give it another year or two before I refinish.