12 replies to this topic

[Swift_General]

I'm thinking ahead to the day my mini's ready to respray and not only can I not decide on the colour but I can't decide what type of paint to use. I am not a professional painter, but have previously resprayed in both cellulose and 2K. I don't have currently have the facility to safely use 2K, which left me thinking I would end up using cellulose, but I have also noticed there is 1K acrylic available and also non isocyanate 2K. I can't seem to find much info on the pros and cons of either though.

Has anyone used either product?

From what I understand acrylic needs a clear coat, however how does it compare to other paints?

Presumably a non isocyanate 2K has disadvantages over normal 2K (otherwise the normal stuff would be outlawed!) so what are they?

[Daz1968]

I have used epoxy primer, solvent basecoat and upol smartclear ready to use 1K clearcoat previously and it has been fine, would rather use this than cellulose,

[Swift_General]

I have used epoxy primer, solvent basecoat and upol smartclear ready to use 1K clearcoat previously and it has been fine, would rather use this than cellulose,

So that wax a 1K acrylic basecoat? Why did you prefer it to cellulose? Thanks.

[Daz1968]

I find it covers better with less coats and easier to get a good finish, but out of choice I would rather use 2k

[bluedragon]

A non-isocyanate based 2K hardener will typically be less durable. It may chip more easily, and possibly (though less likely) fade or discolor more readily. There are 2K paints that have optional isocyanate hardeners (like DuPont Chromabase) and if you read the instructions they only warranty the product if the isocyanate additive is used.

 

That being said, in my experience Chromabase without the isocyanate is still very good. I used it on the lower chin area of a Lotus Elise (which scrapes quite readily) and it didn't peel or chip. It held up pretty well. If the painted surface is well maintained I suspect most 2K non-iso paints will probably stay as good looking as OEM.

 

Many 2K non-isocyanate paints may be sprayable safely using a charcoal filter respirator and reasonable body protection (i.e. cover all your skin, no painting in Speedos and sandals. :) ) Whereas the isocyanate paints definitely require a protective body suit and forced-air respirator. Many people have used isocyanates with just a charcoal respirator, but what they don't realize is that even if you don't get sick or killed the first few times, it is very possible to become intolerant of it and then suddenly you will have the negative reaction.

 

Originally I protected my lungs but left part of my face exposed when I 1st used ChromaBase w/isocyanate hardener. Down the road I started getting these weird burns and rashes. I had no idea where these were coming from, until I finally put 2+2 together and realized it was the isocyanate-hardened vapors that cause the skin burns (took weeks to die down and heal.) They were on my exposed portions of my face and even where spilled some paint on a permeable piece of clothing. Think of what it would have done if it were breathed into my lungs. After complete body protection, no more burns.

 

1K relies purely on time to get the paint molecules to chemically link and harden. This is far inferior, because it can literally take months to truly harden fully. In many cases, it will still be soft or wet to the touch for a day or more after spraying - got to have a clean, dust and insect free place to store the car while this happens. And if dust or insects get onto the wet paint (or you spray too much and get a run in the paint) - you can't repair the damage for weeks or months (until the natural chemical hardening is sufficiently complete.) You can accelerate this if you have a heat lamp system, but if a person had that, they probably would have the gear to safely spray 2K.

 

Cellulose is at the bottom of the list because it dries purely through solvent evaporation - there is no molecular linking of the paint to make it harder and stronger. It is the least durable as a result, both in impact resistance and fading/color fastness. Its one advantage (besides somewhat safer to spray) is that you can repair any errors within a few hours and respray. 

 

However, it's not easy to get an acceptably smooth coating right from the gun. You have to have really good technique, and get the right solvent for the temperature and humidity conditions you are spraying under. (usually there are multiple solvents, often termed "fast, medium, and slow" for different conditions.

 

Thus, most painters end up flatting the cellulose finish and polishing it up (which it is well suited for) to get a good or show-car finish. But that takes a lot of time and labor. And by the way, before you flat and polish the finish, you really should wait at least a week, if not a month or more, before doing so. (perhaps less if you're doing a small spot-repair on a panel or limited area.)

 

Even after cellulose is dry to the touch, solvents are still evaporating from the lower layers of the paint and the paint is still contracting as this happens. Premature sanding and polishing may well result in awful scratches and marks appearing in the finish a few weeks after you did all that labor, as the shrinking paint "pulls back" and causes the formerly invisible polish marks to expand and expose themselves.

 

This is really important to remember when using cellulose primer and primer-surfacer to get a smooth base for paint - naturally you expect to sand primer/surfacer, and if you paint too soon after sanding primer, guess what the paint job reveals after the primer fully shrinks...

[Swift_General]

A non-isocyanate based 2K hardener will typically be less durable. It may chip more easily, and possibly (though less likely) fade or discolor more readily. There are 2K paints that have optional isocyanate hardeners (like DuPont Chromabase) and if you read the instructions they only warranty the product if the isocyanate additive is used.
 
That being said, in my experience Chromabase without the isocyanate is still very good. I used it on the lower chin area of a Lotus Elise (which scrapes quite readily) and it didn't peel or chip. It held up pretty well. If the painted surface is well maintained I suspect most 2K non-iso paints will probably stay as good looking as OEM.
 
Many 2K non-isocyanate paints may be sprayable safely using a charcoal filter respirator and reasonable body protection (i.e. cover all your skin, no painting in Speedos and sandals. :) ) Whereas the isocyanate paints definitely require a protective body suit and forced-air respirator. Many people have used isocyanates with just a charcoal respirator, but what they don't realize is that even if you don't get sick or killed the first few times, it is very possible to become intolerant of it and then suddenly you will have the negative reaction.
 
Originally I protected my lungs but left part of my face exposed when I 1st used ChromaBase w/isocyanate hardener. Down the road I started getting these weird burns and rashes. I had no idea where these were coming from, until I finally put 2+2 together and realized it was the isocyanate-hardened vapors that cause the skin burns (took weeks to die down and heal.) They were on my exposed portions of my face and even where spilled some paint on a permeable piece of clothing. Think of what it would have done if it were breathed into my lungs. After complete body protection, no more burns.
 
1K relies purely on time to get the paint molecules to chemically link and harden. This is far inferior, because it can literally take months to truly harden fully. In many cases, it will still be soft or wet to the touch for a day or more after spraying - got to have a clean, dust and insect free place to store the car while this happens. And if dust or insects get onto the wet paint (or you spray too much and get a run in the paint) - you can't repair the damage for weeks or months (until the natural chemical hardening is sufficiently complete.) You can accelerate this if you have a heat lamp system, but if a person had that, they probably would have the gear to safely spray 2K.
 
Cellulose is at the bottom of the list because it dries purely through solvent evaporation - there is no molecular linking of the paint to make it harder and stronger. It is the least durable as a result, both in impact resistance and fading/color fastness. Its one advantage (besides somewhat safer to spray) is that you can repair any errors within a few hours and respray. 
 
However, it's not easy to get an acceptably smooth coating right from the gun. You have to have really good technique, and get the right solvent for the temperature and humidity conditions you are spraying under. (usually there are multiple solvents, often termed "fast, medium, and slow" for different conditions.
 
Thus, most painters end up flatting the cellulose finish and polishing it up (which it is well suited for) to get a good or show-car finish. But that takes a lot of time and labor. And by the way, before you flat and polish the finish, you really should wait at least a week, if not a month or more, before doing so. (perhaps less if you're doing a small spot-repair on a panel or limited area.)
 
Even after cellulose is dry to the touch, solvents are still evaporating from the lower layers of the paint and the paint is still contracting as this happens. Premature sanding and polishing may well result in awful scratches and marks appearing in the finish a few weeks after you did all that labor, as the shrinking paint "pulls back" and causes the formerly invisible polish marks to expand and expose themselves.
 
This is really important to remember when using cellulose primer and primer-surfacer to get a smooth base for paint - naturally you expect to sand primer/surfacer, and if you paint too soon after sanding primer, guess what the paint job reveals after the primer fully shrinks...

Thanks for your comprehensive reply. I'm not keen on the extended drying times of the 1K, however am keen to look at the non isocyanate 2K if it can safely be used with a respirator. May not be as durable as regular 2K but sounds like it superior to cellulose with no major drawbacks?. Does it require flatting between base and clear do you know?

[Daz1968]

The upol smart clear dries very fast and is easy to polish up next day, I wouldn't touch non ISO 2k it stays soft and reacts with thinner, not good at all in my opinion

Edited by Daz1968, 06 February 2016 - 09:21 AM.

[Stu.]

Cellulose for me every time. Its easy to apply, safe to spray at home and can easilly be repaired / touched up.
 
I know you need to do work with it once its on but I just prefer the finish. Personally I dont like the overly deep gloss finish of 2K and laquers and prefer a more in keeping look to my Minis.
 
It does need work tough - Leaving alone to let the solvents evaporate, flatting back, polishing, clay bar and wax 3 months after with on-going polishing to keep it nice all take up time you dont need to do using 2K.
 
The celly I've applied to mine seems fine and holds up well but a succesful finish is all in the prep before and polishing after. I do use epoxy primer underneath though as it prevents sinking & shrinkage.
 

Edited by Stu., 07 February 2016 - 12:00 AM.

[bluedragon]

Thanks for your comprehensive reply. I'm not keen on the extended drying times of the 1K, however am keen to look at the non isocyanate 2K if it can safely be used with a respirator. May not be as durable as regular 2K but sounds like it superior to cellulose with no major drawbacks?. Does it require flatting between base and clear do you know?

 

 

For durability non-isocyanate 2K is unquestionably superior to cellulose. The need for flatting between basecoat and clear is dependent on the paint system. If it's designed to be a base/clear application, usually not (in fact, many of them forbid sanding the basecoat - they say if you sand it to remove an imperfection, you must recoat it with more basecoat promptly. DuPont Chromabase is like this.)

 

A single stage (non-clear coat) paint would be a different story. You can flat it as needed between coats, or on the final coat (naturally.)

 

However, for these base/clear type systems, the basecoat is really, really easy to spray - without the clear, it looks almost flat (it must have the clear to shine.) Dries quickly and is really hard to get a run or orange peel for the base. For me, almost the only time I need to do anything to the basecoat is to remove some particle that got onto the base.

[bluedragon]

The upol smart clear dries very fast and is easy to polish up next day, I wouldn't touch non ISO 2k it stays soft and reacts with thinner, not good at all in my opinion

 

I think the non-iso results may be due to certain products being poor. The DuPont Chromabase system aforementioned does work well without isocyanate, and is immune to wiping with most any thinner after curing. And I don't think there's anything special or magical about Chromabase, it just happens to be the type I settled on. I have to believe competing paint manufactures have plenty of paint lines that can do the same.

 

I would guess though the cheaper, single stage (intended to be sprayed without clear coat) would be the ones mostly likely to perform poorly. Or a unknown brand with no track record of performance.

 

If trying to pick a brand or system, I'd get the names of what's available from the vendors one chooses to buy from, get their opinion after describing what you want from the paint, then get independent opinions. In general, you do get what you pay for. But you don't have to buy the very best (Chromabase for example is one of DuPont's better paints, but not their top-of-the-line.) But if you go for the cheapest you may well be in for a disappointment.

[Stu.]

Bluedragon, Do you know why topcoats aren't available in epoxy? or are they?

 

I've always thought this would be a good system fo the home diy sprayer but assume it cant be done in anything other than primers?

 

Is it due to issues around chalking or discolouration from UV?

Edited by Stu., 06 February 2016 - 01:47 PM.

[Daz1968]

I would think so as epoxy top coats are not uv stable

[bluedragon]

I would think so as epoxy top coats are not uv stable

 

Yep, epoxy based paints won't maintain appearance exposed to sunlight regularly. A polyurethane paint would have similar properties, but they all require isocyanate activators to my knowledge and are a bit tricky to spray.