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HVLP Paint Systems


Retroanaconda
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Hi all.

I'm going to be needing to be doing some car painting shortly, namely some side panels for my 90, and since I will in the future need to paint most of a 110's body I thought I'd be better off investing in a semi-decent painting setup now than spending a fair amount on rattle cans. I want a decent finish, after all there's no reason a Land Rover can't have nice paintwork and while I am not averse to brush-painting (Series III is partly done like that) a good finish is a lot easier to achieve with spraying.

I've been reading this:

http://www.roverlanders.bc.ca/faq/LRpaintMain.html

He recommends the use of a HVLP (high volume low pressure) paint system, which I have found through some more web research, to not be horrendously expensive. Certainly comparable with a semi-decent compressor et all, with the extra apparent benefits of being more paint efficient and easier to use. So while I could arguably spend the money on a compressor setup and then have the dual-use of that to run air tools etc, I haven't found myself with the need for such things yet, managing quite okay with normal hand tools.

So I've come to look for a HVLP set. Primary use will be painting car body parts, mostly Land Rovers. A search of the forum returned nothing but a few minor mentions of the technology, but with it having been around for a long time I thought someone on here must have used it or be using it for the purpose of car painting?

Can anybody offer me any advice on reccomended makes, specific sets etc? Currently looking along the lines of the Earlex Spray Station HV5000 (see here) which, at £160 doesn't seem to bad to me at all.

Thanks

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Firstly bear in mind that you can get a pretty good finish with a rattle can. Meaning that a spray gun does not have to be that sophisticated to give a decent finish.

I have got an earlex machine and find it much easier than my "proper" compressor and spray gun, less overspray in particular.

As for other uses for a compressor, I use a cordless impact wrench and my air gun is in a box somewhere, it really only gets used for my plasma cutter and tyres.

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Firstly bear in mind that you can get a pretty good finish with a rattle can. Meaning that a spray gun does not have to be that sophisticated to give a decent finish.

I have got an earlex machine and find it much easier than my "proper" compressor and spray gun, less overspray in particular.

As for other uses for a compressor, I use a cordless impact wrench and my air gun is in a box somewhere, it really only gets used for my plasma cutter and tyres.

Indeed you can, and it's the fact that the cost of rattle cans to do my side panels (I want to do the insides too, proper job) would be coming up on a large proportion of the cost of this system, which is causing me to look into it more.

Aragorn: I believe so yes. I am probably going to end up using acrylic enamel paints, as apparently they're easy to use, but I will follow the advice of my local auto paint supplier. The machine comes with a viscosity cup so you can measure it and thin the paint as appropriate.

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From experience I would recommend cellulose, my local paint supplier told me that acrylic was 90% luck and 10% skill, having tried it I would agree. Cellulose is, in my opinion the best paint base available, it remains flexible so will not crack, extremely fast drying so forgiving of flies etc and fast rectification of mistakes. It is also less hazardous to your health than acrylic although as it is absorbed through the skin you do need to cover up, the alternative is lowered blood pressure and stunning headaches. As long as you put a decent quantity of paint on the panels it can be wet flatted to a mirror finish with nothing but patience and 1200 wet and dry. Since it doesn't require laquer there is one less thing to mess up.

You should be able to pick up a second hand 1.5hp 25L compressor and gravity fed gun from ebay for £50-£70, budget a further £80 for primer and top gloss which completes the job for less than the cost of an HVLP system. If you want to be able to use air tools in the future you can sell your kit for what you gave for it and buy a bigger compressor. You will also need an in-line water seperator and filter, do not attempt to spray without one as it'll look great for a while then the water under the paint will expand and cause bubbles. Less important than ambient temperature and humidity is to make sure that you spray at least 2 degrees above the dew point or you will find the paint condenses water as it cools due to the drop in pressure, a decent heater and warming the panels before spraying should sort that out.

Good luck with whatever route you decide to take, any questions then fire away.

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So where does "2K" type basecoat/clearcoat fit into the mix then?

Its my understanding that spraying water based paints (acrylic?) without a proper booth with heaters etc is a waste of time as they wont dry quickly enough.

I think 2K requires a fresh air respirator?

I'm not quite ready to be painting things just yet, but i will be over the next few months, so i'd like the best chance possible of getting a decent job.

I've found that the paint from rattle cans is very brittle and not particularly tough, so when painting panels on the front of the car for example, the paint tends to chip off pretty quickly with road rash. 2K type paint is supposed to be much more hard wearing, hence probably better for something like a landrover? I'd be quite annoyed if i went to the effort of buying the kit (either HVLP or compressor/gun) and spraying the car, and ending up with the same not-very-resiliant paint you get from a rattle can.

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You can get some good finishes with HVLP. I used to use it thirty or more years ago for quick jobs and in fact carried out more than one total respray with it using cellulose.

As in everything to do with refinishing the secret lies in the preparation, good materials and cleanliness. The knack can be learned on bits of scrap.

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2K does require a air fed respirator although some of the new masks claim to be up to the task, personally I wouldn't risk it since you stand a chance of going belly up if something goes wrong and will end up with asthma if you're lucky. 2K has a major advantage in speed of aplication since it has a low solvent content due to the drying being caused by chemical reaction rather than evaporation, this means that much thicker coats can be built up. It is also, as you say, much harder than Cellulose so more resillient. However the kit requirements for it's use and the danger to passers by rule it out for home use. Added to which I prefer the depth that can be gained with Cellulose, but that's more a personal choice than anything else.

Water based paints require an oven, as you say, so are another one for the body shop.

1K Acrylic is the other alternative widely available, it's alright for the odd thing thanks to being available in spray cans, however it is very prone to blooming when damp so not great for a car.

I've never had any problems with longevity when using Cellulose although it does not compare to 2K in it's ability to stay shiny, a decent polish every once in a while will keep it good for years. If you're worried about stone chips then you can either sparay a smooth stone-chip undercoat on the areas prone to damage or laquer the vehicle to give a sacrificial layer that will be easier to rectify. The flexible nature of Cellulose does tend to help in that area too. The real advantage of Cellulose is that it is by far the most forgiving to use and thus you stand the best chance of achieving a really great finish, added to which if you buy a quantity of paint in excess of your needs then touching in points in the future will be no trouble

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As Happyoldgit says above the god is in the detail, with proper use spray cans will do the same job (just with rubbish paint thanks to the ban on Cellulose).

You seem very pro Cellulose... and in the next sentance you say its banned... Is that for all "new" car paint production, or across the board?

Mav

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Theoretically they cannot make new stocks although that does not apply to cars over 30 which are deemed to be classics and thus can use it. Most of the suppliers get around the production problem by calling it Industrial paint, to which the ban does not apply. Halfords and the like just don't make it anymore.

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See, the posts above confirm what i'd previously thaught, that barring the obvious "it might kill you" problem, 2K really does seem to be the best in terms of finish.

Arent there new "2k" type products that dont contain the dangerous Isocyanate compounds that are super-bad-for-you?

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To the best of my knowledge Cellulose paint is worse for you and the environment than modern water-based synthetics (acrylics) though I'd agree it is easier to use, especially if you know how to use fade-out thinners in your top-coat and you are prepared to put more coats on than with acrylics (thinner coats).

Cellulose it porous, the reason car polish came into being. If you can't get an even coat thickeness it can lead to electrolytic corrosion. I like painting in celly but it's become harder to get hold of, bodyshops shouldn't be using it really because of some rules or other.

Likewise for 2k, 2 pack or whatever else it's called. It stayed in use for a long while because of clear on base or 2-stage paints, metallic and micatallic really. The paint colour (stage 1)isn't the issue but the laquer, like with a solid 2k paint, has accelerators and hardners in it. It contain ISOMERS and ISOCYANATES both of which are bad for you. They can be absorbed through the skin, eyeballs and lung tissue. By the time you get the itchy feeling it's too late and you have been poisened. 2-K paints require the use of positive pressure air-fed mask, full body suite and a neutral pressure sealed spray booth with water scrubber on the exhaust air. Once the dust has dried it's fairly inert but any airborn overspray is potentially lethal. To the best of my knowledge.

So I use a meallic (when apprropriate) base coat and 1-k laquer like GIPGLOSS as it requires no mixing. You need to polish it for a high shine and it takes a while to go fully hard but it works really well on plastic trim as it stays flexible without the plasticiser you need in 2-k paint pluss it's great on wheels because it doesn't chip as badly.

I don't use HVLP so I can't comment on ease of use but I know it's meant to cut down on overspray. Because it's low pressure it has less shear force in the nozzle so IIRC the spray pattern is made up of larger droplets of paint therefore it works best with paints that run-out well (slow drying paints where the surface stays fuid). I think it's also more economical on compressor power.

For a compressor you need the biggest you can afford/run of the mains/fit in your shed. A compresosr that runs flat out will wear out, you need a good reserve of pressure to keep consistant results and although a spray gun doesn't need as much air supply as other tools, if you have one and decide to buy yourself some tools then you might end up disapointed with how badly they work. Air saws and DA sanders are amongst the worst.

As said already get a water trap, I use high pressure line from the compressor to my belt where I have a water trap/regulator so that I negate losses in the run of hose and can run an air mast from my belt, the compressor should then be outside of course. Drain the compressor tank regularly too.

If you want to know why you need a water trap I'll show you my Escort, it's covered in micro blisters that took 3 years to surface but now it looks like an adolescent on prom night, covered in zits.

BTW, Halford for one still mixes up in cellulose and their spray cans are pretty good, though for the price you wouldn't want to respray a whole car with them. As a comparison a hobby airbrush will output about the same paint volume as a rattle can, far far less than a proper spray gun set-up.

I'm sure there are professionals who can offer you better advice, I have mates in the trade but I forget half of what they tell me.

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I wouldn't paint a landrover in cellulose its just not hard wearing enough, as a painter the day we stopped using it was fantastic, 2k (2 pack paints) are far superior quality and easier to use.

If i was spraying at home i would look for a LVLP gun (low volume low pressure) less air consumption compared to a HVLP (high volume low pressure)

Water based paints can be sprayed outside they work by having air flow to dry them so put on light coats you can blow them dry with the spray gun where as solvent 2k paints work on the thinners evaporating.

I also wouldn't use 1k laquer as after a period of time with the uv from the sun it will crack up.

Alot of smart repair people use 1k products, you will notice if you see there work it will be shiny when they leave, it will eventually go duller till it cracks up and falls off, they also use 2k with air dry accelerators in this also has the same effect of going duller and flaking off.

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HVLP = High Volume Low Pressure. Type of spraygun. Large volume of air at low pressure - I typically apply basecoat and clearcoat (lacquer)at less than 10psi at the gun compared to 30psi plus with the old guns - means that more paint arrives on the panel than the old systems. Small compressors generally unable to keep up with air demand & you have to keep stopping which is not a good idea.

There are some setups on sale which combine a compressor unit (turbo something?)and gun but I've never used one, only conventional compressor with HVLP gravity feed guns.

With any paint you intend to use you must get the Technical Data Sheets from the supplier. These will give you all necessary information on using the paint e.g air pressure, fluid tip size, amount of thinner/hardener etc.

Cellulose can still be found, esp on ebay.

2k acrylics are in current use. 2K means two component & that's the material itself plus hardener.

You will have either a solid colour or a metallic/pearl/effects colour.

Solids.

Generally you mix the paint with appropriate quantity of hardener & thinner & apply. Usually as 2 coats. Shiny from the gun & with experience & practice no need for further work other than removal of minor nibs.

Metallics/pearls.

(Applied in two stages,the colour coats which dry matt and are then clearcoated over to protect & give the shine.)

Colour coat applied - now usually water based (as in water is the solvent)& hot air blown over panel to flash off the water, movement of air across the panel(s) being required. Solvent based can still be found & heat is used to flash the solvent off. Must then be lacquered - normally 2k lacquer which requires hardener to be added before application. Usually 2 clearcoats.

Just to muddy the water, solids can also be applied the same way as the metallics - base coat then clearcoat.

Single pack clearcoat & non-isocyanate 2-pack clears are available but are generally not as hard - or petrol proof - as iso.

Isocyanate does NOT contain cyanide - a popular myth. It is also absorbed primarily by inhalation of vapour/paint mist not via the skin round the eyes etc. See the attached pdf.

Exposure to any paint mist is not recommended. Occupational asthma is a main risk for professionals. Proper air fed respiratory equipment should be worn.

This is the HSE guide for SMART repairers. As it covers spraying outside a booth I think it is more relevant for the home sprayer

http://www.hse.gov.uk/pubns/web33.pdf

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