Official Luthiers Forum!

45 years ago, when I lived in a very wet cimate in the North Cascades, I used to heat my lacquer before spraying. Simply kept a pot of water on the wood stove, took it off, and set my gun and cup in the water. Worked pretty good in helping me to spray in the rain. Also allowed me to spray coats with more solids, hence, less work. Needed very little thinner or retarder.The last 30 years or so in Hawaii I have alsways been able to wait out a couple of wet days until spray friendly weather came along. Now comes climate change. It's REAL you know! It's getting wetter here, day by day. I never really had any measured approach to using heated lacquer. In those days, most of us just stuck our fingers in the lacquor to test the temp. Pleasantly warm, but not hot, was the target heat range.Unfortunately, today we use gravity fed guns, which complicates the process and involves a lot more transferring of lacquer between containers. However, it looks more and more like I need to try to go back to heating my lacquer if I want to have any kind of relatively constant production. I'm not in a position where I can make a humidity controlled spray booth. I do heat my instruments during the spray sessions and do pump dehumidified air into the booth and that helps. There is also retarder available too, but retarder can have many issues if it is not perfectly controlled. So, anyone heating their lacquer out there? Thanks, Bob

_________________
“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

Haven't for a long time, but I used to have a Crockpot in the spray booth room to heat my lacquer before shooting.

_________________
"Act your age, not your shoe size" - Prince

Curious to learn about this too, I’m spraying in warm, wet weather and getting by with just adding retarder to my mix in various ratios and a few squirts of blush eraser on the odd occasion when that doesn’t do the trick. I shoot with a hvlp turbine which I feel helps a lot in humid conditions because it tends to heat the air stream.

Heating the air stream won't remove the humidity. In fact, part of the reason the air is warm is because it was compressed, and compressed air absorbs moisture....

Heating the lacquer helps it flow out better. Since you can use less thinner and reducer - you put more solids on per coat.

_________________
"Act your age, not your shoe size" - Prince

I guess I was thinking about it in terms of RH being linked to air temp (eg, the same body of air, heated, has a lower RH than when it was cold, since air can hold more moisture the warmer it is). The HVLP turbine doesn’t compress air, it is basically just fan forced (warm) air. That warm airstream - which has a lower RH than the surrounding atmosphere - is what the atomised lacquer is borne in when spraying, and what is washing over the surface of the guitar as the coating lands and the solvents begin to evaporate…

The above is my absolutely uninformed attempt to explain what I was seeing - less blushing when spraying with a HVLP turbine vs conventional compressor and gun

Keep in mind that an HVLP compressor gun steps the feed pressure of whatever spec is (IIRC, close to 40 psi on the Iwata HVLP conversion touch-up gun) down to tip pressure of 6-10 psi or so by expanding the airflow inside the gun, resulting in some cooling and possible condensation of water vapor. Adding an inline desiccant dryer and a water and debris filter to a compressor system is common, with commercial operations using a refrigerant airflow dryer or larger, more capable desiccant system to prevent entrained water droplets from ruining the finish, as well as extending the RH spray range a bit.

The HVLP turbine compression cycle compresses the air less than a standard compressor, and heats the flow up quite a bit in the process (the oldest gun we had did not have plastic grips, and would require gloves after a long session of spray work - ouch!), which has the effect of drying the flow, which provides some ability to spray in a little higher RH without much blush...but it's not as much as you'd think - perhaps 5% or so.

With standard HVLP compressor-fed gun, I could spray with no more than superficial blush at RH of 60-65%; with turbine HVLP, that was closer to a maximum of 70%. Turbine HVLP does that without a water trap or desiccant dryer due to the nature of the turbine compression and lack of a step-down requirement. The warm airflow also heats the finish material in the flow and the receiving surface, further extending the blush-free spray range.

_________________
A constellation only takes shape when one maps the whole.
- Beth Brower

Thanks Woodie, my experience tracks with that - I get minimal blush spraying at RH around 75% - 80% with a turbine, but it requires using more retarder than I like, which is a whole ‘nother can of worms to deal with.

Just as an unscientific experiment today, I heated some almost pure vinyl sealer to about 115 degrees today and sprayed it without blushing at 75% humidity and a temp of around 75-80 degrees. Results were great on a couple of koa ukes, but unfortunately I mixed the sealer into my gun that had a little leftover sealer and retarder in it. Typical 4 stage Fuji HVLP Gravity set-up.That said I won't know until tomorrow if it will go as well with straight sealer or if/how much retarder/thinner might be needed in high humidity.Lots of variables here. Promising though. I learned a long time ago that 1st results that are promising often lead to nothing, so the jury is out at this point.

_________________
“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

Thanks for this. I won’t be spraying for another month or so but will give this a try when I do. What brand of lacquer are you using?

Martin has been spraying at 95 degrees for years and of course a million dollar spray booth , when I was there for training for my repair center they were heating finish Nitro , chemsheen and vinyl. Now after finish spay the use a room that is heated an controlled much like a clean room. So when I set up my spray room I incorporated what I learned there.
I heat my finish to about 120F I use hot water from the tap and place my finish in a glass jar . I use a few heat lamps , one on my gun and one on the body to warm the to about body temp. The mix I use is about 1 oz retarder to a qt and about 4 oz thinner. I do vary a little to accommodate RH . I Have a few guns that I use but that really won't matter much as they are are HVLP and a Turbine.
I also stopped doing more than 3-4 coats a day. let this set 3-4 days level and 2 more coats with a final that I use with a little more thinner and retarder. Let cure for 2 weeks level sand with assilex paper buff and polish The heat helps with the flow out for sure as it helps lower the Viscosity and blushing . Also the surface is so much flatter that sanding time is cut .

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

And you get great results, John. BEAUTIFUL.

_________________
"Act your age, not your shoe size" - Prince

ty the secret is proper filling
I have learned so much this last year

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Josh- I normally use Sherwin Williams, though it is a PITA because it only comes in 5 gallon cans with bungs that don't fit any pour spout I've found. However, the SW dealer is out of nitro right now so I have been using some lacquer from Stew-Mac. Have not used enough of it to know if I like it. The Sherwin Williams works pretty well.

_________________
“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

min wax works good home depot

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it