Better gun

[pcwood]

I have limped along with the cheapo HF HVLP gun for years. it works OK I guess, but I was having a heck of a problem getting a nice varnish finish.
What is a recommendation for a reasonable ( yes some can cost over $1000) gun. Siphon? Gravity? etc?

I use a standard big compressor. I have not really looked into turbine systems.

I used HF guns for a few years but eventually I got tired of how often I had to replace them. They are tough to clean and time consuming. I bought a Mini mite 4 last year and it’s been a huge upgrade.

 

[Henry W]

....
I thought lacquer was bug shells, but I guess now we have acrylic lacquers which are basically similar to poly urethane. I'll try to find some of the Target stuff and play with it. There is always the next project!
....

Scott - (you and others may know all this about differences in products, and if so great; just ignore all this.)
Caveat: New products may have addressed the generalities I describe below (especially polyurethane).

I don't recall the details, except to say that years ago (decade of more?) I chose to strip a multilayer polyurethane finish - unhappy with the finish overall I guess. It was NOT years old, as I recall. Nevertheless, in removal I was able to PEEL separate layers off - not really a desirable property. That made me pay attention to adhesion as described in different ways in this industry - and burn-in is one term used.

Presenting extremes:
Perfect burn-in: Shellac as a resin in a solvent has perfect burn-in - the solvent in the top coats dissolves some of the existing layer and the top coat becomes part of one thick(er) coat (which is why I hate brushing shellac - I work it too much and then have a thick layer of goo... I believe NC lacquers (solvent based) also burn in exceptional well - again I believe the solvent in the top coat partially dissolves the existing lacquer and the whole coat becomes 1 layer.
Does not burn-in: Polyurethane does not burn in at all - each layer cross links within that layer and provides a tough layer with good properties - BUT each layer is distinct and remains so. Layers do not cross link however between existing and new coats, and the adhesion is simply layers sticking to each other (which can work remarkably well). This is one reason that sanding is recommended between coats for polyurethane.

Other coatings likely fall between the extremes. Target Coatings comments on the burn-in characteristics for at least some of their products - especially the acrylic lacquer (6000 series) and CV (9000 series, I think). The acrylic lacquers they describe as having 100% burn-in (under certain conditions?), so the layer do tie in to each other very well. I think the CV does too but under more constraints (time).

Anyways I read the 'similar to polyurethane' phrase and thought it might be true in some respects, but I expect that there are significant differences in burn-in.

Hope that helps.

 

[tvrgeek]

Scott - (you and others may know all this about differences in products, and if so great; just ignore all this.)

I don't recall the details, except to say that years ago (decade of more?) I chose to strip a multilayer polyurethane finish - unhappy with the finish overall I guess. It was NOT years old, as I recall. Nevertheless, in removal I was able to PEEL separate layers off - not really a desirable property. That made me pay attention to adhesion as described in different ways in this industry - and burn-in is one term used.

Presenting extremes:
Perfect burn-in: Shellac as a resin in a solvent has perfect burn-in - the solvent in the top coats dissolves some of the existing layer and the top coat becomes part of one thick(er) coat (which is why I hate brushing shellac - I work it too much and then have a thick layer of goo... I believe NC lacquers also burn in exceptional well - again I believe the solvent in the top coat partially dissolves the existing lacquer and the whole coat becomes 1 layer.
Does not burn-in: Polyurethane does not burn in at all - each layer cross links within that layer and provides a tough layer with good properties - BUT each layer is distinct and remains so. Layers do not cross link however between existing and new coats, and the adhesion is simply layers sticking to each other (which can work remarkably well). This is one reason that sanding is recommended between coats for polyurethane.

Other coatings likely fall between the extremes. Target Coatings comments on the burn-in characteristics for at least some of their products - especially the acrylic lacquer (6000 series) and CV (9000 series, I think). The acrylic lacquers they describe as having 100% burn-in (under certain conditions?), so the layer do tie in to each other very well. I think the CV does too but under more constraints (time).

Anyways I read the 'similar to polyurethane' phrase and thought it might be true in some respects, but I expect that there are significant differences in burn-in.

Hope that helps.

Yes. So much to learn. As the fumes are so bad, I only want to do the kitchen ONCE!

 

[Willemjm]

Scott - (you and others may know all this about differences in products, and if so great; just ignore all this.)

I don't recall the details, except to say that years ago (decade of more?) I chose to strip a multilayer polyurethane finish - unhappy with the finish overall I guess. It was NOT years old, as I recall. Nevertheless, in removal I was able to PEEL separate layers off - not really a desirable property. That made me pay attention to adhesion as described in different ways in this industry - and burn-in is one term used.

Presenting extremes:
Perfect burn-in: Shellac as a resin in a solvent has perfect burn-in - the solvent in the top coats dissolves some of the existing layer and the top coat becomes part of one thick(er) coat (which is why I hate brushing shellac - I work it too much and then have a thick layer of goo... I believe NC lacquers also burn in exceptional well - again I believe the solvent in the top coat partially dissolves the existing lacquer and the whole coat becomes 1 layer.
Does not burn-in: Polyurethane does not burn in at all - each layer cross links within that layer and provides a tough layer with good properties - BUT each layer is distinct and remains so. Layers do not cross link however between existing and new coats, and the adhesion is simply layers sticking to each other (which can work remarkably well). This is one reason that sanding is recommended between coats for polyurethane.

Other coatings likely fall between the extremes. Target Coatings comments on the burn-in characteristics for at least some of their products - especially the acrylic lacquer (6000 series) and CV (9000 series, I think). The acrylic lacquers they describe as having 100% burn-in (under certain conditions?), so the layer do tie in to each other very well. I think the CV does too but under more constraints (time).

Anyways I read the 'similar to polyurethane' phrase and thought it might be true in some respects, but I expect that there are significant differences in burn-in.

Hope that helps.

Burn in finishes, such as Shellac and Nitro Lacquer never really cure fully, as they cure by evaporation only. Therefore they have weak water resistance properties and almost no resistance to chemical cleaners, nail polish remover etc.

Pre-Cat Lacquer, Conversion Varnish and the Urethanes dry by both evaporation and chemical cross linking. They are harder, and offer superior resistance to abrasion, scratching and resistance to water and chemicals. After a certain amount of cross linking (1 1/2 hours for most CV and a little longer for Pre-Cats) there is no burn in, so the previous layer needs light scuffing. On most of the catalysed products you can sand and apply an additional coat within 30 minutes, which means burn in is achieved. The problem with that is you end up with one thick coat which takes much longer to cross link and cure properly.

In production shops, we cannot afford to wait hours for a finish to cure, the whole job should be in and out in a couple of hours, meaning a lot of the hobbyist finishes are not an option.

 

[Henry W]

Burn in finishes, such as Shellac and Nitro Lacquer never really cure fully, as they cure by evaporation only. Therefore they have weak water resistance properties and almost no resistance to chemical cleaners, nail polish remover etc.

Pre-Cat Lacquer, Conversion Varnish and the Urethanes dry by both evaporation and chemical cross linking. They are harder, and offer superior resistance to abrasion, scratching and resistance to water and chemicals. After a certain amount of cross linking (1 1/2 hours for most CV and a little longer for Pre-Cats) there is no burn in, so the previous layer needs light scuffing. On most of the catalysed products you can sand and apply an additional coat within 30 minutes, which means burn in is achieved. The problem with that is you end up with one thick coat which takes much longer to cross link and cure properly.

In production shops, we cannot afford to wait hours for a finish to cure, the whole job should be in and out in a couple of hours, meaning a lot of the hobbyist finishes are not an option.

Thanks Willem - great synopsis.

 

[golfdad]

I have Spray-it guns with 3M cup system. I get a very good finish