Spray Painting Lacquer

[Tenson]

I've never touched a spray gun before. I build nice speaker cabinets and am about to get a workshop with space for a small spray booth. So I am thinking I'd like to get a spray system for applying clear finish. I am unlikely to do much actual paintying, only clear finish. I like a fine satin.

What are the basics that I need to do a good job? I guess air compressor, air filter and gun?

I note many air compressors have a pressure regulator built in - is this enough or do I need to get a seperate one?

Is it possible to use lacquer with no solvent? I hate the fumes and smell of spray cans. I currently use an acrylic lacquer applied by hand and it is water soluble with no smell or fumes - can I spray it?

[ian]

Is it possible to use lacquer with no solvent? in a word NO


I hate the fumes and smell of spray cans. I currently use an acrylic lacquer applied by hand and it is water soluble with no smell or fumes - can I spray it?it depends on how the finish is formulated. What does it say on the can?

[rob streeper]

If you want to do high quality work a good spraygun is a must. SATA and Iwata are my favorites. Devilbiss is pretty good. For lacquer you'll want an airline drier set up after your filter and oil trap.
You also need to select your solvent to suit the ambient temperature(s) at which you plan to spray. Toluene/xylene/acetone mixes are the commonly available lacquer thinners sold in home-stores but they really aren't suited for use at higher temperatures.

[soundman]

Quality spray painting is dependent on clean dry air and consistent pressure.

The cheaper compressors have poor regulators and hopeless water traps.

I strongly recommend using a second reciever ( tank) after your compressor folowed by your main reg then a second good qulaity filter reg. the cheaper compressors you will not have a choice the reg will be fixed to the compressor.


The second reciever will allow the air to slow and cool, this gives the following filter reg a fighting chance to do it's job properly.

As far as non solvent bassed laquer ........ realy such a thing does not exist ........ even the products that are " water borne" use something else as a solvent, often Ammonia or Glycol esters. ... if water was the actual solvent the cured finish would wash off in water.

I have tried some various water borne clear finishes ...... they all come out like jam, thick, glugy, plastic like finishes lack the crispness and clarity of solvent bassed laquers.

The whole point of Laquer is that it is solvent bassed and it works by solvent evaporation ....... their nature means that they can be thinned to rediculous levels 70% thinner in 30% can product is common ...... oil and water bassed reactive finishes can not be thinned anywhere near that far.

The other thing is laquer dries very fast ....... a piano restorer friend of mine reconed they could get 5 full coats of laquer on a piano in a day ... in Melbourne ..... in winter. as long as it wasn't raining.

If you are going to work with laquer, you must have good ventilation, and a good organic solvent respirator is strongly advised.

YES there is a solvent smell ....... but with thinners based laquer it passes very quickly ...... on a warm day with good ventilation 10 minutes ...... where as some of the reactive finishes ( oils varnishes) can be stinking up the workshop for days.

A lot of people seem to be afraid of the solvent smells ...... realy it is not a problem if managed correctly.

cheers

[soundman]

In Australia, the gun most begin with and many never go past is the Star S770 ...... I'd probably say you should think of a HVLP gravity gun like the start S106.
If you are only spraying relatively small pairs of speaker boxes you may be better of with a gravity feed touch up gun ..... these little things only hold 100 -200ml and will spray your last 5 ml of product

cheers

[ian]

Hi Soundman

some good advice in your post, but the OP is located in Kent, England so your comment
The whole point of Laquer is that it is solvent based and it works by solvent evaporation
YES there is a solvent smell ....... but with thinners based laquer it passes very quickly ...... on a warm day with good ventilation 10 minutes ......
might need a little adjusting

[Tenson]

Thank you for the good advice.

I watched a video that suggested a run of piping back and forward to allow the air to cool. Could this act as a cheaper alternative to an extra tank?

If I understand right, the heated air that comes out a compressor will be expanded and thus a pressure regulator directly after the compressor will not be accurate? So I should put a pressure regulator at the handle of the gun?

What is the differnce between a gravity fed touch-up gun and a 'normal' gravity fed gun? Spray pattern size?

I need a little hand holding, please :) Could you give a few example set-ups with parts from online shops?

For example how about this air compressor and filter combo (http://www.sgs-engineering.com/air-compressors/bundles/sc50h-50-litre-high-flow-air-compressor-starter-kit)? Is the 6mm hose dia. enough? Is 9.6CFM enough? Is the 50L tank enough or maybe tank size isn't importiant and only free air output?

I guess I need to give some example of what I'll spray. One thing I will deffinitely spray is flat 1/4 sheets of veneered plywood measuring 600mm x 1200mm. I'll also spray the assembled cabinets. The biggest I currently do is 600mm x 300mm x 300mm but I plan to do some bigger ones like floorstanders.

The lacquer I currently use is this Ronseal (http://www.diy.com/departments/ronseal-interior-diamond-hard-gloss-interior-varnish-25l/176040_BQ.prd?ecamp=Seapla&ppc_type=shopping&ds_kids=92700014019382688&gclid=Cj0KEQjw1ee_BRD3hK6x993YzeoBEiQA5RH_BNOlgDkxH3HANPyIlK9sHPhyBvYD_xYPImu_HuwoB4EaAs798P8HAQ&dclid=COu-ltD7zc8CFTCt7QodzZsIWw) one. Yeah I know it's not a pro product but it actually works really well applied carefully by roller.

What about ventilation, then? Say I have an insulated wooden workshop and a plasterboard booth inside for painting. What do I need to consider? Obviously a decent extractor fan will help. Should I extract from the ceiling or the floor? I guess pulling air downwards can help reduce fumes spreading in the air. Is there any way to stop all my warm air getting out on a cold day? An extractor fan that can be closed off well?

[ian]

If I may, I'll only respond to this part of your post
What about ventilation, then? Say I have an insulated wooden workshop and a plasterboard booth inside for painting. What do I need to consider? Obviously a decent extractor fan will help. Should I extract from the ceiling or the floor? I guess pulling air downwards can help reduce fumes spreading in the air. Is there any way to stop all my warm air getting out on a cold day? An extractor fan that can be closed off well?in part spray booth ventilation is about pulling clean air past the operator and the over spray (and by the very nature of spraying a finish, there always will be considerable over spray) away from the item being painted.
When dealing with the extracted air, you have two basic choices
dump it and the fumes outside, which means also exhausting your warm air to the outside, or
scrub the air to remove the fumes before recirculating it inside your workshop -- however, air scrubbing is typically an industrial scale process, I don't think I've ever seen a DIY air scrubber.

[rob streeper]

Mechanical air compressors always heat the compressed gas to some degree. As the air cools in the tank some of the moisture precipitates out. As the air is released from the tank it cools which causes further precipitation. Coatings with lacquers and oil based paints will suffer if you don't incorporate a drier in your system, something like this: DeVilbiss 130525 QC3 Air Filter and Dryer | eBay (http://www.ebay.com/itm/DeVilbiss-130525-QC3-Air-Filter-and-Dryer-/191898480903?hash=item2cae0a7107:g:hLQAAOSwxCxT~B-e&item=191898480903&vxp=mtr).

If you want a smaller capacity gun this is hard to beat: Genuine SATA Minijet 4400B RP HVLP Gravity Spray Gun Spraygun 1 0mm 1 2mm Cup | eBay (http://www.ebay.com/itm/GENUINE-SATA-Minijet-4400B-RP-HVLP-Gravity-Spray-Gun-Spraygun-1-0mm-1-2mm-CUP-/191672694542?hash=item2ca095370e:m:mS9749S0suzAfOqIiYNIC7g&item=191672694542&var=&vxp=mtr)

Iwata has an entry level model: Anest Iwata w 71 Gravity Feed Spray Gun w 400ml Aluminum Cup 1 0 Tip | eBay (http://www.ebay.com/itm/Anest-Iwata-W-71-Gravity-Feed-Spray-Gun-W-400ml-Aluminum-Cup-1-0-Tip-/232093911924?hash=item3609e00b74:g:gjEAAOSw8gVX5vq5&item=232093911924&vxp=mtr)

[ian]

Some more reading for you ...

This is a spray painting guide from Australia,
http://www.workcover.nsw.gov.au/__data/assets/pdf_file/0009/19584/spray-painting-and-powdercoating-code-of-practice-July-2015-3956.pdf
pages 16 to 24 should give you a grounding in what spray painting involves, and how a small open faced booth might be arranged. Crucially, with an open faced booth, the exhaust fan is mounted in the end wall and needs to be electrically safe in an explosive atmosphere.

[Tenson]

That Iwata W71 gun is my kind of budget, and the CFM looks good to make use of affordable compressors. Other than a smaller spray pattern, is there any other affect having a smaller nozzle? The 1.3mm nozzle looks good with about 7CFM and a spray width of 175mm.

With regards to drying the air; I should imagine simply cooling it to room temp will condense some moisture. After that is a disiccant sillica in-line filter enough? Some suggestions of which models would help - some are £20 some are £400! Do I also need a filter to clean the air of particulate dust?

What line size should I go for? Most affordable compressors have 1/4" outlets I notice.

[rob streeper]

Generally speaking the smaller orifice spray nozzles are used for oil based coatings and the larger diameters for water based. The viscosity of the coating is the driver. I spray lacquer using a 1.0 mm needle/nozzle assembly. I thin canned lacquer by adding 25% v/v temperature range appropriate thinner.
1/4" air line is fine for most spray guns, especially the smaller units. I recommend an in-line particle filter at the gun because dirt can and will get into your airline when it's not in use.
The inline dessicants are fine as long as you refrain from spraying on days when the relative humidity is > 80% or so. You also need to cap the dessicant cartridge holder off when you're not using it, either with caplugs or by installing ball valves on the inlet and outlet ports. I live inTexas and the summer weather here is often extremely dry but I still get condensation in my compressors, Consequently, when I spray lacquer I always use a condensate trap and filter-drier after the regulator on the compressor.

[Ironwood]

I'll admit I am just an amateur when it comes to spraying. But I am happy with the results I get.
I have 3 spray guns, a 1.7mm and 2mm Star S770 guns, which are copies of the Iwata, but still good quality, and a small gravity fed touch-up gun.
For lacquer, I always use the 2mm gun, this has always been recommended by the people supplying the product. I use the 1.7mm for 2pac finishes. Though I do live in a warm climate, I suppose the 2mm helps me keep a wet edge.
I have a 17cfm compressor, it is great for spaying, borrowed a 12cfm from a mate to do a job once, it struggled to keep up.

[rjtwin501]

For most of my projects I use a HVLP (high volume low pressure) spray gun. I purchased a cheaper set of two from eBay and the smaller one I use lots.
Once you get the viscosity settled and at 15 to 18 psi it is like using a rattle can. I use it so much that I have made myself a small portable spray booth using an old box fan fitted it to a largish cardboard box and disposable chux cloth clipped on with paper clips as filters. The turn table I made using an old microwave turn table and tray (easy to clean). I particularly like the finish I get on my final clear coats.My setup is all home made, the compressor is outside in another shed the air is run into my shed using 25mm PVC water pipe with droppers to points around the shed. I then plug in an air filter/regulator and in the glass bowl I put paper toweling to soak up moisture etc. I have made up a shorter hose to connect to my spray gun. I have a panel beater friend who got me started then it was practice and experimenting. I am sure you could get quite technical with paint & mixtures and all that stuff which I am sure is important but I am more than happy with my results and learning more every day. I make small boxes, cutting boards, joinery and toys which are sold at markets on eBay or given away. I also use an air brush for my small stuff
Cheers
John T

[Tenson]

I'm really blown away by all the help! Thanks for the safty guide PDF and also other comments. Interesting to hear recommendation of a larger nozzle for waterborne finish... read on!

I think I am starting to understand a little more.

So firstly let me say I would like to spray waterborne clear coat. It makes my life so much easier with ventilation and cleaning. My reading suggests this is becoming more popular for furnature makers, but does need a differnt approach than volatile solvent based finishes (not to mention rust proof gun parts).

Recommendations on a sprayable waterborne clear coat appreciated.

One thought - if I'm using waterborne finish, do I still need to dry the compressed air? I imagine a bit of moisture will not negativly impact the finish, but of course I still need clean air. What do you think?

I read a very interesting post by someone who said he had been experimenting with waterborne finish on furnature. His conclusions can mostly be summed up in 2 points. 1) The solids in a waterborne finish are suspended, not dissolved. A smaller nozzle helps to brake it up and atomise the finish better. 2) This means the finish doesn't feed through the nozzle so easily, especilly since waterborne finish tends to be more viscous than solvent based lacquer. He recommended use of a pressurised gravity feed cup to keep the finish flowing well at the nozzle. He had noted that with a standard cup, the finish was better wit ha full cup where there was more force pushing the finish down the gun. He also mentioned the pressure in a suction feed cup was only just enough to help the syphon and didn't do the job so well as a pressurised gravity feed.

NOW - lookign for a pressurised gravity feed cup there are only few choises. Those I can afford are the Apollo A7500GT (http://www.sprayguns.co.uk/A7500GT_1.3mm_Atomizer_HVLP_Gravity_Cup_Gun) or Fuji 'M' (http://www.axminster.co.uk/fuji-m-series-spray-gun-ax966270). I could possibly streach to the Funji T75 (http://www.axminster.co.uk/fuji-t70-t75-spray-guns-ax924669). Apollo says it has sime advanced atomization tech. Which would you guys go with? Apollo or Fuji? The Apollo is meant to be more expensive but as you can see the links I found offer a similar price.

Okat also another big question - compressed air or turbine? I see Funji make a 'Mini-Mite' (http://www.axminster.co.uk/fuji-mini-mite-3-platinum-turbine-unit-c-w-t70-or-t75-spray-gun-package-deal-ax928582) system which in total is a similar price as getting an affordable compressed air setup and looks more convinient and portable. It also comes with the more expensive Fuji T75 gun (not sure how different it is than the 'M' gun). What to do, so many choices?!

[ian]

One thought - if I'm using waterborne finish, do I still need to dry the compressed air? I imagine a bit of moisture will not negativly impact the finish, but of course I still need clean air. What do you think?yes
in part successful spraying is about controlling the viscosity of the finish. With an unknown quantity of water in your air line (both as vapour and as drops) I can't see how you can keep the viscosity constant



Okat also another big question - compressed air or turbine? I see Funji make a 'Mini-Mite' (http://www.axminster.co.uk/fuji-mini-mite-3-platinum-turbine-unit-c-w-t70-or-t75-spray-gun-package-deal-ax928582) system which in total is a similar price as getting an affordable compressed air setup and looks more convinient and portable. It also comes with the more expensive Fuji T75 gun (not sure how different it is than the 'M' gun). What to do, so many choices?!
you have two basic choices
High Pressure air as you originally asked about, or
High Volume Low Pressure -- which is the turbine type system you're now asking about.

sorry but I can't really help you choose between the two

[Tenson]

you have two basic choices
High Pressure air as you originally asked about, or
High Volume Low Pressure -- which is the turbine type system you're now asking about.


I don't think it's as clear as that. Many people are using HVLP guns run from a compressor. Provided the volume of air can be deleivered at the required pressure it will work - but what are the pros and cons of each?

For example the Iwata W71 gun manual kindly indicates how many CFM are needed for the various nozzle sizes. A 1.3mm nozzle with gravity feed needs about 7CFM. I can get a compressor that is rated at 9.6CFM (what pressure?) so should mean my tank never empites.

[ian]

But it would probably mean that your compressor was running continuously.

Typically small compressors like the one you are referencing are more suited to pumping up tires and operating an air nailer, rather than spray painting.

[Tenson]

What would be a good entry level air compressor for the Apollo A7500GT or Fuji T75 Gravity gun?

Given the size of what I need to spray I doubt I will paint for long streches non-stop.

[rob streeper]

I've only used one turbine pumped HVLP and I didn't like it. The unit I used was made by Titan and it had a 5 stage turbine. The gun was drippy, leaked paint, the compressor was loud, the gun got unpleasantly hot, the gun and hose were heavy, hard to adjust and a lot of work to clean. Sata makes a pressure feed reservoir and regulator that can be added to any of their guns, mine is on the right in this picture.

396971

Iwata also makes a pressure fed gun but I can't locate a link for you at the moment.

[ian]

Given the size of what I need to spray I doubt I will paint for long streches non-stop.Even a medium sized speaker box might take 1 to 2 minutes to spray, and with a small compressor and receiver, it's probable the compressor would cut-in 10 to 15 seconds after you activated the gun.

I can't at the moment find it, but I recall BobL posting some comments about the limitations of small compressors not so long ago.

[Bohdan]

With a reasonable gun it should take no more than 15 secs to paint a speaker box and this would have pauses while you rotate the box.

[Tenson]

I think I have come to a decision. I'll probably go for the Fuji T75 gun with their mini-mite turbine. Yeah I know... after all the questions I want to get an off-the-shelf system!

Here is some of the things I've been thinking about.

1) If dry air is so importiant, why do the turbines (even the rather pricey ones) not have a filter to remove moisture?

I think the answer to this is to do with pressure differential. When a compressed gas expands, moisture is condensed from it. The bigger the pressure difference on expansion, the more likely moisture will consense. So when we have a compresser with air in the tank at a whooping 100PSI or more and we allow it to expand, first at the pressure regulator and then again at the gun nozzle, moisture will certinaly condense if there is any in the air. The large pressure differential from 100PSI to atmosphear is why it becomes super importiant to take out the moisture before-hand. When we talk about an HVLP turbine the air is never compessed more than about 16PSI and so when it expands at the gun nozzle there is far less likelyhood of condensation forming, even if it is held in the air. That I think is why we don't see much effort made to dry the air from HVLP turbine systems. Compressing the air just creates a problem that needs to be fixed.

2) If HVLP guns work at a lower pressure and have the same cap size, how on earth can they use more air volume? You have a cap with say a 1mm hole and the air pressure behind that hole will dictate the air quantity that passes. This was really confusing me.

I think the answer is simple. The cap size is not what restricts the air flow - the gun needle is. So I guess an HVLP gun will have a larger diameter needle than a conventional high pressure gun, even if the cap size is the same. Is that right?

3) Why are HVLP turbines spec'd at something like 100CFM even when the guns never use more than 20CFM?

I guess the answer is that turbine CFM is spec'd at free flow into atmosphear? Is that right? So when a gun forces the turbine to work at a pressure of say 20PSI, the max. air-flow the turbine can provide will reduce significantly, probably to something like 40CFM.

4) Waterborne finishes have solids suspended, not dissolved, so they need more pressure to atomize well. Surely a conventional high pressure gun will work better?

I think this may well be the case. However for myself I just don't want the overspray a high pressure gun gives in my small workshop. The cap size and gun design will also affect the atomization so pressure is not the only consideration.

Okay then, I hope laying out my thoughts might help someone in the future! Please add anything you think I've missed or got wrong.

Simon

[ian]

Hi Simon
a bit more reading for you

Exhausting Overspray in the Home Shop - Popular Woodworking Magazine (http://www.popularwoodworking.com/techniques/finishing/exhausting_overspray_in_the_home_shop)

HVLP’s evolution is an interesting story | Woodshop News (http://www.woodshopnews.com/columns-blogs/finishing/501453-hvlps-evolution-is-an-interesting-story)

Spraying Right, Spraying Safe, Where to Use Your HVLP Sprayer @ The Finishing Store News (http://news.thefinishingstore.com/index.php/spraying-right-spraying-safe-where-to-use-your-hvlp-sprayer/)

[Tenson]

Thank you! Something for the evening there.

[homey]

Hi Tenson,

For interest you might like to check YouTube where there are several noise level comparisons between the various Fuji HVLP systems. This may not be an issue for you, but could be worth 5 minutes to view anyway?

cheers,

Brian

[Tenson]

I've heard the Fuji Mini-Mite is rather noisy, but the 'Quiet' versions are a lot more pricey! I suppose I could get the Fuji or Apollo gun and a differnt turbine but it doesn't seem very cost effective and I'm not sure other turbines are better?

For others who read this thread - I've had recommendations for Morrells (a UK brand) and Sayerlack water based lacquers for spraying. Sayerlack especilly seem to offer a lot of range.

[rob streeper]

Simon,

Please let us know how it goes with whatever system you choose. I've looked at the Fuji an Apollo systems too, but my underwhelming experience with the Titan put me off of the idea of a turbine.
One of the things I know you'll find is that the output of the turbines is hot, you can't escape the laws of physics. When you compress a large volume of air in a short period of time you get heat.
To me the water based lacquers are rather like vegetarian bacon - poor imitations of the original. Nonetheless I'm interested to hear of your thoughts of the system and coating you do end up going for.

Cheers,
Rob

[Tenson]

I'm sure I'll be back here when I get the system. I've got to get my workshop first!