Thank you. I hate to ask something that may already have been answered but I'd like to have this confirmed: can one paint directly on the polyurethane finish or is a regular primer layer required?
I consider the clear to be more of a sealer/primer. For the highest level of smoothness, another layer will not hurt.
So, prime with solvent based clear urethane. Then apply several spray coats of Armorseal. Let this dry and cure for a day or so and then sand smooth.
Apply several finished coats of Armorseal. enough to do the colour sanding and polishing without cutting through. Let this dry and cure for a few days.
So, prime with solvent based clear urethane. Then apply several spray coats of Armorseal. Let this dry and cure for a day or so and then sand smooth.
Apply several finished coats of Armorseal. enough to do the colour sanding and polishing without cutting through. Let this dry and cure for a few days.
Looking at spray guns for an air compressor, there are many available with a big range in price. They start at around AU $30-40 and I can't see anything wrong with them. Suction feed.
Anything wrong with this?
http://www.transquip.com.au/product.aspx?ID=210&PARENT=477
Or there is gravity feed:
http://www.transquip.com.au/product.aspx?ID=208&PARENT=477
HVLP are more expensive:
http://www.transquip.com.au/product.aspx?ID=137&PARENT=118
My questions:
1. What is the downside of using the cheaper units?
2. Is there any significant difference between gravity and suction feed?
3. Is HVLP better or just suited to a different application?
I'm tempted to just get a $40 suction feed unit from Bunnings, but is this a bad idea?
Anything wrong with this?
http://www.transquip.com.au/product.aspx?ID=210&PARENT=477
Or there is gravity feed:
http://www.transquip.com.au/product.aspx?ID=208&PARENT=477
HVLP are more expensive:
http://www.transquip.com.au/product.aspx?ID=137&PARENT=118
My questions:
1. What is the downside of using the cheaper units?
2. Is there any significant difference between gravity and suction feed?
3. Is HVLP better or just suited to a different application?
I'm tempted to just get a $40 suction feed unit from Bunnings, but is this a bad idea?
A good gun starts usually at $250 or at list it use to. The differences are wast for a professional but not so much for a beginner. The materials used in construction directly related to the longevity of the gun. There are acid catalyzed finishes that require SS internal parts for example. Cheap guns are not likely to last but then again, you are not opening spray shop.
The spray pattern aren't going to be as refined, more orange peel type effect.
Adjustments will be more rugged and some may not work.
So, basically the downside is that you looking at more work down the road.
HVLP like anything else has it's own advantages and disadvantages. HVLP from air compressor with a nice size tank beats HVLP from turbine blower.
Gravity caps are generally better until you have to spray something upside down.
The spray pattern aren't going to be as refined, more orange peel type effect.
Adjustments will be more rugged and some may not work.
So, basically the downside is that you looking at more work down the road.
HVLP like anything else has it's own advantages and disadvantages. HVLP from air compressor with a nice size tank beats HVLP from turbine blower.
Gravity caps are generally better until you have to spray something upside down.
paulspencer said:
I wouldn't recommend suction feed. The gravity guns are, like for like, better. Plus you need a higher cfm compressor for suction.
Curiosity got the better of me and I bought a cheap and cheerful no-name gun off ebay a year or so ago. Didn't do a bad job at all considering. Wasn't as good as the £220 Anest Iwata guns I use but hey, it only cost £30 so you can very easily forgive that.
I bought a Harbor Freight gun yesterday for $39.95 on sale plus an additional 15% off--$33.96 final cost. It is model 43430 and has a pretty good reputation and following on the internet among amateur users. I will report after I use it in a few days to paint some doors and a baffle for my center channel.
Ray
Ray
Thanks for the replies. I had a look at a few yesterday. It brought up a few more questions:
1. Is the amount of air required ever going to be an issue?
2. What size container is best? I was thinking around 1L
3. Are HVLP better? If I understand, then it seems they are better made so that they can deliver the same amount of paint with less air so there is less waste of paint. Is there anything else?
4. How are gravity feed better?
1. Is the amount of air required ever going to be an issue?
2. What size container is best? I was thinking around 1L
3. Are HVLP better? If I understand, then it seems they are better made so that they can deliver the same amount of paint with less air so there is less waste of paint. Is there anything else?
4. How are gravity feed better?
paulspencer said:
Lets see...
Its always an issue. Air is the life of the gun, if it doesn't have enough and its not clean then the finish suffers.
Most cups are 750ml. Don't get a huge one because, when full, they get heavy on the wrist real fast as you'll find out when you start spraying for any length of time.
Careful its misleading to read too much into what the marketing suggests. HVLP isn't the ideal spray system.
HVLP systems, as the acronym suggests, use greater volumes of air but this is supplied at a lower pressure. The lower pressure means less over-spray and a gentler spray action. What HVLP is really about is material efficiency - it lays down more paint on the work and less goes into the air. However it isn't any better on a finish quality level than the common RP (Reduced Pressure) systems. HVLP guns also use up lots and lots of air because like I said, they don't rely on pressure, they rely on sheer volume. A regular compressor doesn't hold much air (100ltr is probably the average receiver size_ but they work because they supply small amounts of that at high pressure - its their modus operandi. HVLP works opposite to this so you won't have much luck here unless the compressor is over 5hp or ideally 10hp with a big 200ltr+ receiver tank - very expensive. So what to do? HVLP really favours turbines which are a mixed bag in themselves. These push lots of air at low pressure and are ideally suited to HVLP guns. Sound perfect right? Well no because if you buy a cheap one then all you get is something to paint the fence with and if you want a paint shop quality turbine then you'll need to spend quite a bit so its expensive for the good stuff. Another thing worth mentioning is that turbines don't take up nowhere near as much room as a large and capable compressor.
A great alternative for the hobby market without the high price tags of a good or professional HVLP setup is LVLP. These guns work on modest compressors of 2-3hp with 50ltr+ tanks and produce exceptional results. The problem now is the guns themselves are expensive. One of the best LVLP guns around is the Anest Iwata LPH 400 LV:
http://www.anest-iwata.co.uk/catalogo.asp?Area=1&cat=2
Aside from that there's always good old RP or conventional guns, these rely on relatively small volumes of air but high pressure. These have been around for decades now and are very much perfected. The air caps and general fluid/air channels are very sophisticated on the professional models and deliver an immpecable finish with mid range compressors and good paint product.
Which would I go for if it were me? LVLP for a casual DIY'er or RP for higher throughput. I use RP currently with Anest Iwata W400 WB guns and a 4hp compressor with 100ltr tank.
It all depends on the manufacturer, the compressor, the paint and the whole caboodle really. But consider that none to all of these may be true when citing gravity fed superiority over suction:
- Less parts, simpler and hence more reliable
- Less air consumption because nature does the work rather than more air being used for the suction system.
- You use all the paint product in the cup
- More consistent feed rate
paulspencer said:
Paul,
1. Yes, the amount of air available can make a difference. You need not only sufficient pressure, but volume as well. The HVLP guns generally need less of the above, but a small compressor will tend to cycle more often leading to increased wear. Besides, air tools (sanders, impact wrenches, etc.) are so nice for all kinds of things that it would probably be better to get a "BIG" compressor first and save the regrets.
2. The container (cup) on the Gun? In the States, most regular spray guns are a quart, I guess that a liter would be normal in the rest of the World. There are smaller guns (detail guns), that are used for smaller jobs and touchup work.
3. HVLP isn't better per say, but it operates on far less pressure and consequently produces, I'd guess 80% + less overspray or mist in the air. Far less wasteful of, what is now, pretty expensive paint and it's also safer and healthier. There are HVLP guns that are also junk, just like the siphon feed guns can be if cheaply made, but one type isn't necessarily superior to the other.
4. Gravity feed lets you use just about every last drop of paint in the cup, as it drains into the gun. Remember that expensive paint? The commercial guys don't like to toss unused paint away. I personally like the balance of the "Underslung" or suction feed type of gun, but HVLP guns can come this way as well, often called "conversion guns".
I hope some of this is of value.
Best Regards,
TerryO
Thanks for the help Ant and Terry. I'm now leaning towards gravity feed and I'll stay away from HVLP. I have access to a compressor so I'll have to check the specs on it before I buy anything.
In looking at spray guns, I've noticed they come with different nozzles. One online store sell two together with different nozzle sizes 1 and 1.4mm. Is one gun ok for sealer, colour and clear finish with automotive acrylic paints? Is there a particular nozzle that is most likely best?
I've found one gun which looks good - gravity feed 600ml pot and 1.4mm nozzle, 50psi max pressure. Does this sound like a good choice based on the numbers?
Has anyone used spray putty? Is it useful in this kind of work?
I've found one gun which looks good - gravity feed 600ml pot and 1.4mm nozzle, 50psi max pressure. Does this sound like a good choice based on the numbers?
Has anyone used spray putty? Is it useful in this kind of work?
I've since bought a gun. When I opened it I found it was HVLP! Oh no! 
There was nothing on the outside to suggest that, and the sales guy seemed to know less than me. He gave the kind of answers that say "I have no idea really, but this is my job and I have to say something, so this sounds safe enough. The more expensive gun is better."
However, the compressor can supply twice as much as the maximum required air flow. I think I'm pretty safe.
A few questions about spraying. When spraying the sealer, you say sand every few coats. How much dry time do you allow before sanding? If you are doing 15 coats, sanding every 3 and waiting a day before drying, then that means 5 days and cleaning the gun 5 times just to get to the colour!
Then with spraying the colour, would that be around 2 - 3 coats? Do you sand at this point after these coats?
You seem to put a lot of emphasis on getting the sealer nice and flat, but not the colour. I'm wondering what the difference is.
I had been thinking that spraying with automotive paint meant that all the spraying was done in one day, and that there was no wait in between spraying coats.
What polisher to do you use?
There was nothing on the outside to suggest that, and the sales guy seemed to know less than me. He gave the kind of answers that say "I have no idea really, but this is my job and I have to say something, so this sounds safe enough. The more expensive gun is better."However, the compressor can supply twice as much as the maximum required air flow. I think I'm pretty safe.
A few questions about spraying. When spraying the sealer, you say sand every few coats. How much dry time do you allow before sanding? If you are doing 15 coats, sanding every 3 and waiting a day before drying, then that means 5 days and cleaning the gun 5 times just to get to the colour!
Then with spraying the colour, would that be around 2 - 3 coats? Do you sand at this point after these coats?
You seem to put a lot of emphasis on getting the sealer nice and flat, but not the colour. I'm wondering what the difference is.
I had been thinking that spraying with automotive paint meant that all the spraying was done in one day, and that there was no wait in between spraying coats.
What polisher to do you use?
What kind of finish have decided to use in the end?
Brand and type (such as Camble Cristal or Ilva 000 series poly for example. )
Brand and type (such as Camble Cristal or Ilva 000 series poly for example. )
I'm after high gloss, I'd call it piano gloss but I'm not sure that's technically correct. As glossy as I can get, as smooth and mirror like as I can get. I'm after metallic red and black on two separate parts.
I also have a few other projects I plan to spray - white furniture and kitchen cupboard doors. I'll probably do them first as practice as I'm not as fussy with them.
I intend to use the automotive paint recommended by the local automotive paint supplier. No idea about brand. I think it was an acrylic water based paint. I'll have to go back and check. (I haven't made the boxes yet).
I've actually condensed all the info in this thread down into a word document. I did it for my own use, to keep relevant comments together. When I've had some experience with it, I might put together a tutorial.
I also have a few other projects I plan to spray - white furniture and kitchen cupboard doors. I'll probably do them first as practice as I'm not as fussy with them.
I intend to use the automotive paint recommended by the local automotive paint supplier. No idea about brand. I think it was an acrylic water based paint. I'll have to go back and check. (I haven't made the boxes yet).
I've actually condensed all the info in this thread down into a word document. I did it for my own use, to keep relevant comments together. When I've had some experience with it, I might put together a tutorial.
Anybody have experience using Dupont's Imron polyurethane finish?
It has a very high gloss and covers well. Dupont sells a clearcote that adds even more gloss.
http://www.mikeandjerrys.com/dImron.asp
It has a very high gloss and covers well. Dupont sells a clearcote that adds even more gloss.
http://www.mikeandjerrys.com/dImron.asp
Carl_Huff said:
Carl and others reading this,
Dupont's Imron, and in general all of the activated paints, are good for gloss retention, durability, etc.
However, if you aren't an experienced pro, with purpose built paint booth, positive pressure respirator and the rest of the (usually) required protective equipment...
DO NOT USE THIS PAINT!!!!!
When this this stuff first hit the market 30 years or so ago, a lot of experienced painters used this paint just like all the other paints that they had used for their whole career...ONCE!
That one paint job was also their last one. These commercial paints are for professional facilities that employ extensive and very expensive protective systems. This stuff is deadly and can kill you, not over a lifetime of use, but the first time.
Here's the data sheets with the whole story, direct from the horses mouth:
http://www.performancecoatings.dupont.com/dpc/en/us/html/prodinfo/daf/US_en_GNRC_12-0_RFN.pdf
Stick to one part paint, it's very good and a whole lot safer.
Best Regards,
TerryO
Terry,
Not that I am questioning your expertise but what makes this paint so dangerous to work with? When I had looked at the warning and use labels it looked to be similar to the risks that one takes when doing hand fiberglass layup. What am I missing?
I know that this paint is very popular when painting the chassis of show and custom cars. I understand too that it is very popular when refinishing private aircrafts.
Please tell me more?
Not that I am questioning your expertise but what makes this paint so dangerous to work with? When I had looked at the warning and use labels it looked to be similar to the risks that one takes when doing hand fiberglass layup. What am I missing?
I know that this paint is very popular when painting the chassis of show and custom cars. I understand too that it is very popular when refinishing private aircrafts.
Please tell me more?
Actually I was recommended to get thinner, hence would I be right in saying it would have probably been lacquer based?
Carl_Huff said:
I'm not Terry, but...
Isocyanates in the hardener are very bad news. They are found in reduced concentrations in regular 1K polyurethane, but the amounts in 2K urethane auto paint are dangerous. You really need to protect yourself with the proper breathing apparatus (fresh air feed) and contain the overspray. It's pretty much illegal to spray this stuff out in free air.
Not to down play the danger of sniffing polyester resin, it is not the same beast. It uses organic peroxide as the hardener.