conor1n
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Do you expect to spray jotamastic through that?!
I do anyway.... it says its a 2.5mm tip.
Do you think it's not suitable?
Do you expect to spray jotamastic through that?!
I’m a fan of Jotamastic but spraying it you’ll get orange peel as it is a thick high build primer. I use 80 as I find it sprays the easiest, lays the flattest and just apply an extra layer. Automotive epoxies will lay flat if you spray them properly so for places like engine bays you could apply a good automotive epoxy and then topcoat directly without sanding but if spraying Jotamastic you will need to sand it flat. Jotamastic is very surface tolerant so is a good first layer and is how I use it. Whack it on, flat, fill/high build if needed and then seal with an automotive epoxy. I really like the Mipa epoxy, it sprays lovely and is easy to sand.How well does this jotamastic spray?
Just looked at the data sheet for jotamastic 90a winter grade, I will be doing it in January with small heaters on so likely around 12c no hotter.
According to the data it needs a pressure pot at 2100 psi?! I will be brushing underneath but all the engine bay, interior, exterior needs to have a good primer finish to save hundreds of hours sanding brush marks! I have a 1.8 hvlp gravity fed gun....
You won’t spray everything under a car. Even on a rotisserie you want to get the brush out and get all the hard to get places first. This is Jotamastic 80. If the car is assembled and on the ground you will do a much better job with a paint brush and if you thin it it will lay nice.I do anyway.... it says its a 2.5mm tip.
Do you think it's not suitable?
I don’t like having lots of different layer materials but it sounds like you’d be better off with sandable primer (polyester or high build or both) over a couple of layers of epoxy. Seems like you need to work out how best to attack the job.Well if it sands no problem then I'm happy to use it instead of an automotive variant, the benefits seem to outweigh the extra effort in prep and considering its an old rusty shell and not new panels, I'm sure there will be tons of flatting and prep to be done so may actually help fill some pits that normal epoxy won't?
Really annoying they don't sell a 1 litre tin as I'd be happy to try spraying it and if it doesn't work just use it underneath with a brush.
I wonder if they do a tester set
What makes you think I would be better with a filler primer? If the juton is a nightmare to sand i actually don't mind, as it won't be me doing the sanding haha thats for the boy to do!
“considering its an old rusty shell and not new panels, I'm sure there will be tons of flatting and prep to be done”.What makes you think I would be better with a filler primer? If the juton is a nightmare to sand i actually don't mind, as it won't be me doing the sanding haha thats for the boy to do!
I will chip in with my limited experience of Jotamastic 90.
I have only used 1 can of Jotamastic 90 with winter grade hardener on a few projects (driveway steel gates, lathe chip pan etc.) and here are my observations:
1. It is not the easiest to spray, I had to experiment quite a bit with my spray guns to get a semi decent finish.
2. On my first try I could not get a good finish with a paint brush or roller (probably did not thin enough/did not warm the paint up).
3. Warming the paint helps a great deal when spraying.
4. Mine took ages to cure - I would suggest 7 days is probably accurate for the paint to be decently hard.
5. It is really tough stuff once cured, I love it.
I am pretty sure I sprayed with 2mm nozzle size but it might have been 2.5mm.Thats helpful, thanks.
May I ask what ended up being the best setup to spray with? Tip size, thinning etc?
Would you say that the mipa Grundierfiller is going to act as a good sealer or should I use a normal non high build epoxy first to seal the steel?“considering its an old rusty shell and not new panels, I'm sure there will be tons of flatting and prep to be done”.
Fresh Jotamastic doesn’t sand well, it clogs. There’s products that are made to build and sand if that’s what is needed. If using Jotamastic direct to metal then get it on and leave it for a good while. It will then sand not too bad with 80 grit. I’d the move onto automotive products. Jotamastic is just too slow once you’re into the bodywork. There’s other more suitable epoxies that can be sandable primer fillers and sealers. How well your primer sands will dictate how flat and smooth your finished topcoat will be.
There’s plenty of good car epoxies out there. Mipa Grundierfiller is what I use and think it’s great; cheaper and a much easier product to use and less work as it sprays so much better and can be top coated or sanded pretty quickly. It lays down lovely compared to Jotamastic.
Polyester is hygroscopic, epoxy isn't.fillers are hygroscopic
The slow hardener E25 is thicker so builds better and the fast E10 thinner so flows out better so works well as a sealer. Always epoxy direct to metal for me and I seal with epoxy before topcoat.Would you say that the mipa Grundierfiller is going to act as a good sealer or should I use a normal non high build epoxy first to seal the steel?
I don’t think that’s an issue these days and I don’t wet sand. I use the Mipa 4 + 1 high build but it gets sanded right back and coated over with epoxy but it can also be used as a wet on wet sealer coat mixed 3:1 with 30% thinners.Polyester is hygroscopic, epoxy isn't.