Time windows for clearcoating over basecoats

[gphood]

With solvent basecoats, the general rule of thumb (that I'm aware of) is to clear once it's flashed off (15 minutes or so) when there's the maximum amount of solvent still in the paint to provide adhesion with the clearcoat. However, sometimes I want to do a bit of airbrushing first so it could be a few hours before I eventually get to clearing. Can I have some opinions about the maximum time people allow before they really need to get on with clearcoating?

Secondly, for those using waterborne basecoats, how is adhesion achieved if there's no or very little solvent in the paints? How much time do I have to put artwork on before I need to start clearing? I'll be be moving over to waterborne over the next 12 months so I'd like to be aware of that sort of thing before I change over.

Thanks for any info you can provide - all in aid of my ongoing paint and clearcoat education :)

All the best

[Dream Weaver]

Hi Grant
The advice I can give you is on my own experiences , and from talking to paint reps. Your rule of thumb for clearing is right , But depending on the product you are using , you can actualy have up to a 8 hour window with no problems. I am a die hard dupont lover . If using dupont bases, and clearing with a 7500s clear , the window can be pushed to 12 hours safely. If you have to take more time for completing art work , a suggestion is to give the base colour a chance to set , then give the surface a scuffing with a red scratch pad before muralling this will give you all the bite you need for clear afterwards. The only problem that you could run across , is when using bases with a lot of metalic or metal flake in it. Then scuffing could disturb some of the metal flake. Since i get a lot of commissions ahead of me , and some with fresh base colours , one thing that has saved me alot of troubles , I get my shop to lay a good coat of clear over the base , that way your window is taken care of. Then I just wet sand the future work , and do the airbrushing, and not worry about time.

As far as waterborn base coats, here in Canada they are just starting to introduce them, But I'm assuming the process would be the same. Hope this helps.

[ABD]

Like DW..If i plan on ABing...I like to get a coat of clear on my base..Just so it's protected, i can put that out of my mind and just deal with the artwork.

..........As far as windows...I wasn't aware you could go as long as DW suggested with certain Uros??.....If i miss my normal flash time, i wont touch it again without letting it cure and sanding first...Kandys, flakes you really can't sand directly on without risking damage, So i plan accordingly to make sure i will not miss my window..I get at least a coat of clear on to protect my precious Base, hahaha!

Sorry i don't have much experience with Waterbase, i dare not touch that one.

[gphood]

Thanks DW.

Since moving to where I am now and not being able to find a bodyshop who could do the clearcoating either well enough or quickly enough for me I decided to start doing it all for myself. I've not got ideal working conditions for it really but I was all out of options. I try to keep my clearcoating to a minimum so I do as many stages as I can before applying it. Not ideal, I know, but you work with what you've got.

I do use scotch pads to give the base a key if it's going to be a long job. If it's a job with lots of airbrushing though, it's effectively putting a fresh coat of basecoat over the top so I find I'm working within that time window again as the newly airbrushed artwork can't be scotched up without ruining it.

My clearcoating is improving all the time though, especially thanks to some of the information I've been given on here.

[Dream Weaver]

Abd the window that i was talking about , the 8 hour one , comes from the dupont paint rep , and so far in 18 years not a lift chip or seperation yet.............or do I just have golden horse shoes up my ass lmao. But you are definately right about damaging kandy's and flakes with sanding or scratch pads. Those always get a clear first before i mural them. And you are right about missing that friggen window ABD, if you miss it , you have to sand it .

[gphood]

Thanks DW & ABD for your replies.

With regard to solvent basecoat, I know you can re-activate it by spraying fresh basecoat over the top of it so you have your maximum time window again, but how about spraying a very fine mist coat of straight thinner? Is there any reason why that wouldn't work? You could re-activate airbrushing then as well presumably.

Any thoughts?

[Cowboy]

Hey Gp, I wouldn,t suggest that as for the correct chemical bond it,s more in the base then the reducer. ( It,s not like the old laquers where you could burn it back in ) IMO .

If You have to sand Your base for any reason I would suggest rebasing it no matter whether it,s solid or metalic,s. Just so You dont have streak marks in it. because of it drying flat, They dont ussually show up untill the clear is on, by then it,s to late.

I Allways used Dupont Chroma base & 7600,s for clear, which is a speed clear. Just use the right temp reducers for Your conditions & You should be fine, Same way with your bases . You can ussually pour it on wet with no runs or sags Then follow with Your other coats.

I allmost allways waited to right at 30 minutes before clearing to allow it to gas off , As to not trap any solvents escaping thru the clear. This Is Just what has Worked for Me. So Just My opinion. Good luck. Cowboy

[Clinton]

"They" say you have a window of up to 24 hrs, but in reality you should clear as asoon as posable after flash off. Like the others have said if you going to AB on it lay a coat of clear down after flash off and scuff it, that's the bast way to make sure you get a good bond.

Dreamweaver, water bourne clear has been around here for at least the last 12 years. We still have some of the first stuff out, that's hw good it was.:angry-smiley-030: They are just starting to come out with something that actually works.:)

[Dream Weaver]

Hi Clinton
Good point buddy lmao. In this neck of the woods, they just avoided it like the plague . But from what I'm hearing , they want to bring this waterbourne base and clear in with a vengence. I guess they really don't car much about custom paints , and are more concerned with the inviroment. My resto shop guy says , they are figuring on three years to to fully introduce water bourne into all body and restoshops................should be interesting lmao

[Clinton]

Yep it's been coming for years just got booted in the butt by the public now. I've been restoring cars for 16+ years now and it's always going through changes for enviroment reasons. I've been working with AA for the last 2 years as well as a few other water bourne/based paints so it really wont effect my work a bunch. It's just getting used to what you have to work with really.

[Dream Weaver]

true true Clinton . I'm so glad my clear coat shop takes care of that . I used to do all my own clear coat up util about 11 years ago .Found this great restoration shop that does all my clear coat , for a price that is unbelievable . The give me a double clear and buff, the work turns out awesome. It was not even worth my time to buy all the products, and saved a whole lot of pain and expences.Now I can concentrate stricly on the art side of it. I send him work , he sends me work , great arrangement.

Guy

[Stang]

Not sure if this was mentioned but It's cheaper to use an intercoat clear (PPG DBC 500 might be 5000 don't remember, HOK SG 100) between your art. It's basically the same as the base only clear. Dries as quick as the base and you're ready to sand and airbrush. Then go over it with whatever clear of choice.

[jason prouty]

i solely use urethanes and send out all my clear and have for the past 14 years, in some cases the stuff doesn't get cleared right away, most in 24-48 hours, but sometimes up to a week.....never had an issue, my bodyshop guys will shoot innercoat to wake up the paint, i'm sure you technical gurus will eat this up and i'm sure the manufacturer says no no no, but it works

[Clinton]

i solely use urethanes and send out all my clear and have for the past 14 years, in some cases the stuff doesn't get cleared right away, most in 24-48 hours, but sometimes up to a week.....never had an issue, my bodyshop guys will shoot innercoat to wake up the paint, i'm sure you technical gurus will eat this up and i'm sure the manufacturer says no no no, but it works

Nope that's just another "right" way to do it. The intercoat is the same as the base just no pigment so it will bite in and allow that "window" again. It's just like spraying another coat of base on top.

[jason prouty]

i thought it must be ok, because most of the bodyshops i work with do the same thing, i don't know a whole lot on the technical side, i usually just depend on my bodyshop friends to the right thing, i've been pretty spoiled, i usually don't need to anything more than wipe it clean when it shows up and sign it when i'm done

[PinWerk]

i use hok urethane clears or autobody master clears, i'd always used their tech sheets for open windows. if i dont have any tech sheets like on the autobody master urethane clear, i waited like 10 min or mainly and all the time i do the finger test, check for whether its sticky or tacky and i go by that before i spray my other coats, whether flow or regular coats. can't go wrong by the finger test

[colourshift]

Good to know for clear coat novices like myself...thanks.

[colourshift]

but then, I base ...usually...with AutoAir, no window...and then graphics over the top...again, no window...clear...voila. Pretty.

[PinWerk]

hey colorshift.. i'd never dealt with AA. give me some insights do you have to heat activate the bases of aa in order to use say urethane clear on top?? thought about tryin out the AA paints.. i have their paint chart around here somewheres but i got tons of paint books n etc layin g around.. theres no tellin where its at. recall something about heat activating it.. n was wondering about it..