Thread: Hercus lathe, paint hardening?

Hi Ken,
Some are just content just to watch it dry.You obviously have a greater need to wait for it to go hard.

In the link below the blurb says they bake their baked enamel at 180F .A quick look at my thermometer suggests thats around 70C.

Do ovens go that low?

heres the link

http://www.huskyliners.com/signpastfaqs.html

Grahame

Can you be a bit more specific.

Exactly which primer and epoxy did you use? There are more than one variation available

How many coats of the primer did you apply?
how long between coats did you leave before the next coat?

Same with the epoxy top coat
How many coats? how long between coats?

Can you leave a a mark in the surface with a finger nail?

These paints should be as good as they are going to get in less than a week even if it was cold and wet when you did the job.

I doubt whether forcing it to dry in an oven would be of any use now you should get the same effect if you put them outside in the sun on a hot day. but as its been several months there should have been plenty of hot summer days to more than cure the paint even left inside.

In response to Durwood, and being more specific, I have used a mixture of undercoats.

Where one or two small parts were concerned, they were undercoated with Dulux Quitrust metal primer in a spray can. I used the spray can to save 20 minutes or so cleaning the spray gun, a bugger of a job.

Where half a dozen larger parts were concerned, they were undercoated with Dulux Quitrust etch primer, applied by gun.

All parts were given several coats in the one sitting, be it by can or gun.

Several coats of Dulux Quitrust epoxy enamel were applied in the one sitting after a period of at least 24 hours.

As mentioned, all parts have been allowed to air dry in a warm room for up to several months.

After this time, I can leave a mark with my finger nail, if hard pressed.

Sounds like baking won't make any difference, however I might contact Dulux to ask, something I should have done, but didn't think of it.

Thanks to all for the advice.

Ken

Answer it pretty simple. you have massively overdone it with the amount of material you have applied, Far too many coats, far too soon.


I think if you check the instructions on the can you will find they suggest only a couple of coats tops. These paints rely on the material being able to react with the air and for the solvent to evaporate out of the wet coat.If you put more than two coats on at a time it is impossible for the underneath coats to cure as they are protected from doing so by those on top.

There is NO paint made which could cope with the conditions you have subjected them too. Paints are made as a final layer over a surface to give protection. Normally the total layers of paint and primer is only equal to about the thickness of a about 3 to 4 thousands of an inch ( about the thickness of a couple of bits of paper.

If you want a perfect surface you need to use other methods to get it smooth not paint. Paint is not meant to be used to fill areas deeper than mentioned though there are primers that are made to fill Etch primer isn't. I think I have read that you used primer, then plastic filler then primer then colour. As a set of steps thats Ok but it would be one coat of primer no more than two , thats one pass with a gun or can.

When its completely dry plastic fill (several times if necessary before any more primer, once smooth, 2 coats primer and when dry sand any faults that show up touch up if you rub through with primer (little as possible.)

If the surface is good two coats of colour, leave 20 min on a warm day between coats Never more than 3 leaving 20 minutes or more before next coat. If you stuff it up leave for a month and rub and apply one more. Normally if you stuff it up after the 2nd and try to fix it with a 3rd and its still crook then you wash it off with its solvent and try again hopefully not doing what you did to stuff it first time round. Thats a lot quicker than waiting for it to dry enough to rub and do again, days/sometimes weeks.

Even with 2 pack paints which go hard right through in hours these same rules apply, they can be sprayed on thicker as they have hardener and will go rock hard but its too expensive to be used instead of plastic filler to fill a hole/dent /fault. Heating 2 packs reduces the time they cure from hours down to less than an hour. but you can't go higher than 70 C especially with plastic filler in the mix. Actual baking enamels are heated to 200 C- or more (just like powder coat) but you need special gear for them and the surface has to be near perfect ( no fillers -even lead)

When spraying one coat means the gun goes over the surface once (thats a coat) not one to the left one to the right then back again) that was three coats.

Your paint eventually will go hard but it could be several more months. If I was given your job to correct I would tear it all off start again and it would be dry hard in a matter of days not months.

I'm surprised that the top coats didn't actually wrinkle up as can happens in such cases. the top coat drys out and the solvent still present in the underlying coats then attacks the top coat resulting in a finish similar to applying paint stripper. Being epoxy based probably stopped that happening.

Hi Durwood,

Sounds like you know the paint game, a very informative answer.

The coats I applied were whisker thin, to avoid any runs, so I reckon I've done the right thing.

The final finish I achieved looks fantastic to me, I will definately not be repainting this lathe in my life time.

Your comments are appreciated.

Ken

Originally Posted by neksmerj

Hi Durwood,

Sounds like you know the paint game, a very informative answer.

The coats I applied were whisker thin, to avoid any runs, so I reckon I've done the right thing.

The final finish I achieved looks fantastic to me, I will definately not be repainting this lathe in my life time.

Your comments are appreciated.

Ken

Ken

Seems to me you have nothing to lose by sticking a few bits into the oven to see how it goes.

Chuck a cake mix in as well and you can have morno's when the lathe is finished.

Try a dead low heat and fan forced if you can.

You risk the paint blistering if you put them in an oven, if you think you have to try - one small piece and if it stuffs up you won't have much to repair. Out in the sun would be far safer and even that may blister the paint if it is as soft as you say.

Not a good idea to use any oven that would then be used to prepare food in to dry paint, unless you like the flavour of paint in your cake.

Prehaps should also mention normal stoves are not suitable to dry paint in besides the obvious odour household ovens are entilely different to paint drying ovens. If you have a domestic oven you will need to make changes to its construction so it could be used to dry paint. Use the wifes oven and you risk a fire or explosion.

On a normal oven the heat is mainly kept in the oven and circulated to keep the temperature constant. If you put drying paints in it the solvent being evaporated off can't escape quick enough so the paint doesn't dry much if at all. all evaporating solvent must be expelled as it comes off. That means the heat must be constantly replaced by newly heated air.

It would also be possible for the fumes to ignite if there was a source close to hand so a gas heated oven would be out. Gas ovens for paint use a heat exchanger. They heat a sealed container which the air passes over so the flame is isolated from the paint. An electrical element would work better but it would be possible for elecric wires or a spark to ignite the fumes so they are out also. they also must be set up in a heat exchanger.

The heat only helps the drying process if solvent needs to be dryed out of the paint or hardener is present and the heat will help speed up the chemical reaction. once past those points it is of no great value. though paint will cure quicker if the temperature is warm than if its low.