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Airbrushing larger areas to a gloss finish & Community Call to Action!

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  • Member since
    March, 2019
Airbrushing larger areas to a gloss finish & Community Call to Action!
Posted by Nezil on Tuesday, March 05, 2019 1:11 PM

Hi guys, I'm new to the forum, and somewhat new to airbrushing, but wanted to post some of my findings regarding achieving a gloss finish on auto bodies...

The Issue

I was fortunate enough to have my employer have a need to purchase an airbrush and compressor setup for a project, which when completed migrated to my house. Since I was in charge of the project, I was able to choose the parts we bought, and selected an Iwata HP-CS and Paasche D3000R.

I've now completed two models (Ducati 1199S Tricolor & Honda / Acura NSX) and am working my way through two new kits (Carrera GT & Toyota 2000 GT), and whilst I've found the HP-CS to be great for some of the smaller parts in auto kits, I've been struggling to get a consistently glossy finish on the larger parts like bodies and the chassis.

The issue that I feel I'm having is that the HP-CS simply doesn't flow enough paint. In order to achieve a gloss finish, it's important to have a consistent wet coat over the body, and this involves more paint than a 'dusting'. It also requires that each pass with the air-brush overlaps the previous, and that the previous hasn't dried before you do the overlap.

I discovered Mr. Color Levelling Thinners a few month back, and whilst the added retarder in this thinner helps significantly, I'm still struggling to achieve the level of gloss that I think is possible.

I should say that when applying 2K clear, the issue is reduced because the drying time is significantly slower than lacquer paint, but the issue is still present in the form of increased orange peel.

One other point worth noting is that the insufficient paint flow can also result in a rough sandpaper like finish in concave sections like wheel wells because the 'window' of pressure, distance and paint flow is smaller.

Working out a Solution

I selected the Iwata HP-CS because it was highly recommended for model making, and whilst I'd 100% agree that it's a great airbrush, I've come to the conclusion that it may not be ideal for scale auto modelling...

I cannot understand why maximum flow rate and spray pattern are not part of airbrush manufacturer specifications, but set about trying to test these factors for myself. Measuring spray pattern size is difficult, and I've not yet found an objective way to test this (though I have some thoughts), but maximum flow is quite easy.

The test I came up with was to load 2ml of 91% IPA into the colour cup, and then time the duration it takes to empty this under full trigger at 15 PSI. I had previously bought, but barely used, the 0.5mm needle / nozzle / cap for the HP-CS, and had a brand new 0.35mm needle / nozzle set as well as an older, damaged (trumpetted) but still functioning 0.35mm needel / nozzle set to test with.

My results (which I'll detail lower down) showed that though counter intuitive, the 0.35mm needle / nozzle set flows more paint than the 0.5mm needle / nozzle set! I also found that the old worn out and trumpetted 0.35mm nozzle flowed a lot more than the new one, which was probably to be expected.

Although I'd purchased an Iwata HP-CS, many of the scale auto modelling YouTubers, particularly those in Europe, were using and recommending the Harder & Steenbeck line of airbrushes. I won't deny that I fancied trying something new anyway, but was at least hopeful that the Harder & Steenbeck brush would flow more paint and so placed an order for an Infinity CRplus 2in1 with 0.2mm and 0.4mm needle / nozzle / cap sets.

My Results & Conclusion

Without further ado, here are the results of my objective maximum paint flow testing:

  • 42 seconds - Iwata HP-CS brand new 0.35mm needle & nozzle (~0.05ml / s)
  • 50 seconds - Iwata HP-CS almost new 0.5mm needle & nozzle (~0.04ml / s)
  • 20.5 seconds - Iwata HP-CS old, trumpetted nozzle & nozzle which still sprays OK (~0.10ml / s)
  • 19.2 seconds - Harder & Steenbeck brand new 0.4mm needle & nozzle (~0.10ml / s)
  • 55.3 seconds - Harder & Steenbeck brand new 0.2mm needle & nozzle (~0.04ml / s)


So it's pretty obvious that the Harder & Steenbeck airbrushes flow a hell of a lot more than the HP-CS, and in fact the 0.2mm Harder & Steenbeck needle / nozzle flows nearly as much as the HP-CS 0.5mm needle / nozzle!

I'd already painted the body of my Carrera GT by the time I got my new airbrush so I cannot fully report on if the extra flow achieved my goal of easier gloss on large areas, but I can already say that it's much easier to paint concave areas and large areas of decanted TS-29 semi-gloss black; the Carrera GT chassis plate for example.

Going Forward

As I said earlier in the post, I cannot understand why maximum flow data is not available for airbrushes, but felt that this might be very valuable for us modellers.

I've provided the data above for the entire Harder & Steenbeck 0.2mm and 0.4mm needle / nozzle sets (all Harder & Steenbeck airbrushes use the same needles and nozzles from the Ultra to Infinity), and the HP-CS 0.35mm and 0.5mm needle / nozzle sets, but these are the only airbrushes I have.

I thought about buying the 0.6mm Harder & Steenbeck needle / nozzle set but I cannot justify the expense having just bought the Infinity airbrush.

I'd like to open this up to the community though, and have therefore created a public Google Docs spreadsheet that's editable by everyone. Conducting the test is quick and easy, so please consider contributing to the effort and filling in some data on other airbrush / needle combinations. I think we could all benefit!

Spreadsheet link here: https://docs.google.com/spreadsheets/d/1c-4cmwrlagSfVg84IWSIO9MQPuh_ESpdP_6nSO7ZNiU/edit?usp=sharing

  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Wednesday, March 06, 2019 9:40 AM

Nice data gathering. It's an interesting project with potentially useful results. I have already found your info useful, as I've been considering a new gravity feed airbrush (my current one is a 40 year old Badger 200IL siphon feed) and have been looking at the Iwata HP-CS and the Harder & Steenbeck Infinty CRplus. I was concerned about sufficient flow rates with the H&S, but your data shows significant flow. I also was not aware that the H&S has a 0.6 mm needle/nozzle option.

I can't view the google spreadsheet due to corporate net nanny intervention (I'm on a work computer). I was also going to post a link to Don's Airbrush Tips site, but the net nanny wouldn't let me visit it. However, you might find it worth checking out as he compares many different airbrushes, especially the Badger line. I don't think he does flow rates, but he does do spray pattern tests and gives useful opinions and specifications.

Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.
       - Antoine de Saint-Exepury

Trevor

  • Member since
    March, 2019
Posted by Ozzy_GNGR on Friday, March 08, 2019 12:18 AM

Great post. I will test with my Paasche Talon 0.66 mm and 0.38 mm and post the results. Thanks.

  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Friday, March 08, 2019 9:32 AM

During the test, is the needle backed out all the way (maxiumum paint flow)?

Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.
       - Antoine de Saint-Exepury

Trevor

  • Member since
    March, 2019
Posted by Nezil on Friday, March 08, 2019 10:04 AM

Bainford

During the test, is the needle backed out all the way (maxiumum paint flow)?

Yes, just as far as the trigger will go back, nothing more than that. 
  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Friday, March 08, 2019 3:12 PM

Nezil
 
Bainford

During the test, is the needle backed out all the way (maxiumum paint flow)?

 

Yes, just as far as the trigger will go back, nothing more than that. 
 

OK, got it. I was going to give this a try to add to your data, but my airbrush is single action. The best I would be able to do is wind the needle most of the way out.

Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away.
       - Antoine de Saint-Exepury

Trevor

  • Member since
    March, 2019
Posted by Nezil on Friday, March 08, 2019 3:57 PM

Ah yes, good point, I hadn't thought about single action, but it's a very valid choice for large areas.

Yes, I'd suggest you try exactly that. Set the needle where you'd consider to be maximum you'd ever use.

  • Member since
    March, 2019
Posted by Nezil on Friday, March 08, 2019 3:59 PM

Ozzy_GNGR

Great post. I will test with my Paasche Talon 0.66 mm and 0.38 mm and post the results. Thanks.

That would be great data to have. Before I bought my Infinity, I was considering a Talon. I like the fan head attachment and would love to try it out some time.

  • Member since
    March, 2019
Posted by Nezil on Friday, March 08, 2019 4:05 PM

Bainford

Nice data gathering. It's an interesting project with potentially useful results. I have already found your info useful, as I've been considering a new gravity feed airbrush (my current one is a 40 year old Badger 200IL siphon feed) and have been looking at the Iwata HP-CS and the Harder & Steenbeck Infinty CRplus. I was concerned about sufficient flow rates with the H&S, but your data shows significant flow. I also was not aware that the H&S has a 0.6 mm needle/nozzle option.

I can't view the google spreadsheet due to corporate net nanny intervention (I'm on a work computer). I was also going to post a link to Don's Airbrush Tips site, but the net nanny wouldn't let me visit it. However, you might find it worth checking out as he compares many different airbrushes, especially the Badger line. I don't think he does flow rates, but he does do spray pattern tests and gives useful opinions and specifications.

Thanks for your kind words!

I'm quite familiar with Don's Airbrush Tips site, and have found it quite useful. You're correct that he doesn't test flow rates, and his spray pattern tests are really focussed (as are almost everyones) on how fine a line he can achieve. This isn't particularly useful for the application of gloss coats to large areas, but I can see that it has value to many of his readers.

  • Member since
    March, 2019
Posted by Ozzy_GNGR on Friday, March 08, 2019 11:52 PM

Here are my test results:

  • Paasche Talon 0.38mm: 34 seconds (~0.06 ml/s)
  • Paasche Talon 0.66mm: 6 seconds (~ 0.33 ml/s)

0.66mm Talon is like a firehose :)

  • Member since
    March, 2019
Posted by Nezil on Saturday, March 09, 2019 1:10 AM

Ozzy_GNGR

Here are my test results:

  • Paasche Talon 0.38mm: 34 seconds (~0.06 ml/s)
  • Paasche Talon 0.66mm: 6 seconds (~ 0.33 ml/s)

0.66mm Talon is like a firehose :)

Thanks Ozzy, I've added your details to my spreadsheet.

What's interesting here is that the 0.38 of the Talon is somewhat similar to the 0.35 of the HP-CS (0.06 ml/s vs 0.05ml/s), which stands to reason because 0.38 is slightly bigger than 0.35...

The 0.40 Harder and Steenbeck and 0.50mm HP-CS flow rates looks like an anomoly if you plot a chart of needle size vs maximum flow with an exponential trend line:

I realise that there is no-where near enough data to draw any conclusions yet, but what I can say is that the 0.40 Harder and Steenbeck nozzle sets flow a lot more paint than would be expected for their nozzle size, and the 0.50mm HP-CS nozzle set is very strange because it flows less than the 0.35 set in the same airbrush!

  • Member since
    March, 2019
Posted by Nezil on Friday, March 15, 2019 11:43 PM

I couldn't justify it, but I did it anyway... bought a 0.6mm needle / nozzle / tip set for the Infinity.

I've added the results to the spreadsheet, but duplicating here for easy access, and this time in order of maximum flow:

  • Harder & Steenbeck 0.2mm: ~0.04 ml/s
  • Iwata HP-CS 0.5mm: ~0.04 ml/s
  • Iwata HP-CS 0.35mm: ~0.05 ml/s
  • Paasche Talon 0.38mm: ~0.06 ml/s
  • Harder & Steenbeck 0.4mm: ~0.11 ml/s
  • Harder & Steenbeck 0.6mm: ~0.26 ml/s
  • Paasche Talon 0.66mm: ~0.33 ml/s

Updated chart as well:

 

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