Experienced sprayers: advice needed

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
Hi

I need some advice about finishing from people in the know.

I recently finished up some spraying on some cabinets, left them a week and then sanded flat and rubbed out and this was the result:

[IMGDEAD]http://server3.uploadit.org/files/zeroex2-asdf.JPG[/IMGDEAD]

[IMGDEAD]http://server3.uploadit.org/files/zeroex2-flred2.JPG[/IMGDEAD]

Looks great there but 2 weeks on the gloss look has faded and somewhat duller looking. I used 1K primer, along with single pack base coat, pearl coat and 1K acrylic laquer.

The finish is also still soft as evident by the finger nail test and this is 3 weeks on since spraying.

Do I really need to be using 2K primers and 2K urethane clearcoat to get better results? And exactly why would they be better?
 
ShinOBIWAN said:
Hi

I need some advice about finishing from people in the know.

I recently finished up some spraying on some cabinets, left them a week and then sanded flat and rubbed out and this was the result:

[IMGDEAD]http://server2.uploadit.org/files/zeroex2-flred.JPG[/IMGDEAD]

[IMGDEAD]http://server3.uploadit.org/files/zeroex2-flred2.JPG[/IMGDEAD]

Looks great there but 2 weeks on the gloss look has faded and somewhat duller looking. I used 1K primer, along with single pack base coat, pearl coat and 1K acrylic laquer.

The finish is also still soft as evident by the finger nail test and this is 3 weeks on since spraying.

Do I really need to be using 2K primers and 2K urethane clearcoat to get better results?

did you use enough hardener? are you in a humid climate
 
Re: Re: Re: Experienced sprayers: advice needed

ShinOBIWAN said:


Non of the paints I used need hardener.

The UK isn't a humid climate.


ah... I see no reason why it would be soft after 3 weeks... though lacquers do take more time than the norm to fully harden (from my experience)

lacquers do dull somewhat... but nowhere in the time you're talking about...

:xeye: hmmm
 

Cortez

Member
2002-12-26 9:45 am
Hungary
I guess, the result is up to the used materials quality.
There can be a lot of difference between 1K lacquers too.
For example the cheaper furniture lacquers are commonly soft.
Expensive 2K lacquers are likely harder.
Sometimes when the drying time is not enough between coats,
can be cause similar results.
 
A couple of thoughts

First off how hard is the material below the finish?

If you have a sample do the same fingernail test.

If I had to guess your problem I would say that you have a materials problem. THe primer or the filler are reacting with the top coats.

You did a good job on the finish from what I can see from the pics. So give it some time to cure out. If in a couple of weeks you have the same problem you have but one ugly choice.

:devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr: :devilr:

Repaint and thin no more!

Seriously you have to remove the finish and do it again. I had a job like this about 16 years ago. My first real experience with piano black. I admit I lost.

The second time I did the same colour I was alot smarter. I did all the prep work with two part fillers and then sealed the whole thing with epoxy. No problem after that!

If you used a scratch filler that is premixed my guess is that is what is causing all this grief. I swore the stuff off 15 years ago!

Mark
 

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
Thanks for the suggestions so far guys.

To answer your questions:

I used a two part automotive filler where needed.

The primer was water based MDF primer with 1K primer over that. Reason for using two was to stop the MDF soaking up gallons of expenive 1K primer.

Redoing actually isn't a problem since I'm rebuild the entire cabinets again after changing some drivers and cabinet shape accordingly.

It could well be that that I didn't allow enough flash-off time between coats.

I did something last year in high gloss black and I've done nothing different this time around, except of course use different colours. That project dried and hardened well - finger nail test passed after around a month.

I think what I'm going to do this time around is skip the water based MDF primer, go with 2K primer and clearcoats. With around 15 minutes between coats.

Any other suggestions would be appreciated.
 
I'm always surprised at how long acrylic lacquer takes to harden. I've twice made the mistake of leaving knobs resting on panels several days subsequent to finishing, and thy've 'sunk' into the surface and spoilt it :-(
If the haze is just on the surface, try polishing with a 'metallic' grade automotive cutting compound - I've had excellent results on all sorts of finishes, including 1950s cellulose, which comes up better than new.
 
originally posted by mwmkravchenko
If I had to guess your problem I would say that you have a materials problem. THe primer or the filler are reacting with the top coats.

You did a good job on the finish from what I can see from the pics. So give it some time to cure out. If in a couple of weeks you have the same problem you have but one ugly choice.

I believe that what mwmkravchenko said is all true, unfortunately.
If the laquer hasn`t hardened after a week there is a bigger problem.


originally posted by ShinOBIWAN
The primer was water based MDF primer with 1K primer over that. Reason for using two was to stop the MDF soaking up gallons of expensive 1K primer.

I´m not a chemist (but sprayed quite a lot of speakers) but I feel that combining the water-based with the 1k stuff likely was responsible for Your problem.

I`d never ever mix/combine different kinds of laquer systems.
I wouldn´t even mix laquer from the same basic system (water-based, 1k, 2k etc.) and different manufacturers.
IMO You can get all kind of wierd effects from doing this.
This is particular true for 2k.
For a durable and good looking finish I`d go for a 2k filler/ primer/ hardenener/ laquer/ thinner system from ONE manufacturer.



originally posted by ShinOBIWAN
The primer was water based MDF primer with 1K primer over that. Reason for using two was to stop the MDF soaking up gallons of expensive 1K primer.


I think what I'm going to do this time around is skip the water based MDF primer, go with 2K primer and clearcoats. With around 15 minutes between coats.
I`d say that just primer is not enough to fill the holes of the MDF.
This is just too thin and You`d need too much of it to get the surface smooth.
For this there is "filler" (as the name implies already).

I`d do it this way: filler->"coarse"-sanding->filler-primer->fine-wet-sanding->basic-laquer->clear-laquer.
There are different ways/systems for 2k basic-laquer/clear-layquer. One way is to do these two coats "wet in wet" and to use hardener for the last coat only (the clear-laquer).
The other way is to use hardener for both, the basic and the clear laquer and to wait with spraying the clearcoat until the first coat has fully hardened.
I prefer the second method as it`s easier to apply a thicker coat of the clear laquer (what looks better IMO) while avoiding "noses".

BTW:
Most of the failures that I had with 2k spraying speakers resulted from not following the manufactorers instructions really closely and I learned from this that sometimes it`s better to actually read the instructions AND to follow them.

Detailed instructions may differ somewhat from one system and from one manufactorer to another and I´d strongly suggest to buy all that stuff You need in a good shop where there are familiar with what they sell. Somewhere You can explain what exactly You want to do and where they can give You detailed instructions what You can do with the material and what better to avoid.

Also be aware of not using laquer/hardener etc. which has been stored for a long time (particular when cans has been opened already). If I open a can I note the date on it.
If You happen to use lets say an overstored hardener with Your last clearcoat this might not only spoil Your entire spray job but You loose quite a bit of money too.

This 2k laquer stuff is just too expensive to waste much of it.
 
Do not ever mix paints from different manufacturers!

That is the problem!

It is a very bad idea to mix different paints. THey have different formulations of thinner and catalyser. I wasn't familiar with the brand names and paid no attention to them before.

Also acrylic laquer takes longer than 15 minutes between coats for proper curing. If you got away with it before ask yourself what time of year did you do it? What were the humidity levels.

I worked for a company and sprayed nothing but acrylic laquer for 8 months every day. The temperature the humidity all made a difference in the finnish. The hazy colour that you showed is water that is trapped in between layers. If it is ever to cure you have to bake it. In the sun or under some hot lights. Be carefull not to burn it!

Mark
 

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
Mark & cocolino

Sorry guys I think my explanation was a little off, I haven't got a moisture problem. When I said the finish had dulled I simply meant that glossy finish I had for the first few days after rubbing out had faded, not gone frosty as would be evident if moisture was a problem.

You were both right on the money with your sumation regarding different manufacturer's - I actually have 5 different products on there from 4 different manufacturers:

1st MDF Primer (Akzo Nobel)
2nd Grey Primer (Halford)
3rd Black Groundcoat (Rage)
4th Pearl effect coat (Rage)
5th Clearcoat (U-Pol)

So as you can see there's a lot of different manufacturers, along with water, cellulose and acrylic based products.

When I had decent success last year I actually only used the waterbased MDF primer and the basecoat and clearcoat were from the same manufacturer. So 2 different manufacturers in 3 different coats.

Although I did fully follow the manufacturers instruction which stated leave 5 minutes between coats.
 

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
richie00boy said:
Ditch the celly product(s) and stick with the acrylic and I think you should be fine with the water based MDF primer. I think you'll still need the dedicated MDF primer as a base for normal (automotive?) primer due to the absorbency.


RobWells said:
What about using fibreglass resin as a sealer on the mdf ? Could roller it on with a small sponge roller...

Rob

Cheers for the replies fellas,

I can actually skip the MDF primer without worry about paint absorbtion by using wood hardener resin.

Unfortunately when I built these I hadn't actually discovered it, so they never got done. Testing on scrap bits shows good results for spraying straight over.