A 'how to' for High Gloss Finishing

[454Casull]

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?

[454Casull]

^

[MJL21193]

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.

[paulspencer]

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....210&PARENT=477

Or there is gravity feed:
http://www.transquip.com.au/product....208&PARENT=477

HVLP are more expensive:
http://www.transquip.com.au/product....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?

[R-Carpenter]

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.

[ShinOBIWAN]

Originally posted by paulspencer
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....210&PARENT=477

Or there is gravity feed:
http://www.transquip.com.au/product....208&PARENT=477

HVLP are more expensive:
http://www.transquip.com.au/product....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?

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.

[Ray Collins]

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

[paulspencer]

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?

[ShinOBIWAN]

Originally posted by paulspencer
Thanks for the replies. I had a look at a few yesterday. It brought up a few more questions:

Lets see...

1. Is the amount of air required ever going to be an issue?

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.

2. What size container is best? I was thinking around 1L

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.

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?

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.

4. How are gravity feed better? [/B]

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

[TerryO]

Originally posted by paulspencer
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?

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