JayZeus wrote: ↑Mon Jan 16, 2023 11:58 am
I’ve always used either Rustins MDF sealer or a 1# shellac wash coat before painting MDF. Will be interested to hear your feedback once you’re happy.
I always used mdf edge sealer or sanding sealer before. But I always found finishing the edges time consuming.
I decided to change the water thinning ratio down to all mdf primer and zero water to see how the gun coped with that mix.
Gun 50psi and 1.5 jet and all primer sprayed ok with a narow fan 6" from the work piece. Obviously the spray volume was alot less than before, but manageable all the same.
Will continue like this for 3 doors and see how things progress. Drying is quicker with this mix.
Unfortunately my DeVilbiss gun bought for automotive use isn’t suitable for water based applications. I might look at something else to add to the toolkit for such purposes next time a project helps justify it.
Don’t know why it’s not suitable, but the literature with the gun said so. It’s one of the Finish Line, FLP-3 maybe. Perfect when I’ve sprayed 2 pack finishes for bikes, cars and boats.
Sounds like you have a good system setup anyway to get the finish down. Always interesting to learn what works for others too. Another possible solution in the back of the mind for when a problem comes up!
After much deliberation on the water based primer, I've decided on the following.
The ability to add water as the thinner material is great, and it sprays well. Where it falls down for me is the drying time. Its too long for me. Possibly the current climate and low temperatures are probably not helping. Although I constructed a makeshift spray booth that is well sealed and has a 2000watt fan heater on inside it, and its nice and warm.
I tried various different water/paint ratios and found that a 10% mix sprays well enough, and a higher water ratio sprays better, but with less depth coverage.
If you could allow the time in a heated area for the primer to fully dry, its probably ok. It drys hard enough to be handled without smudging the coating, but this needs about 2+ hours first.
Under normal circumstances I could have double coated, sanded and top coated 8 doors today using pre cat finishes.
Using this waterbased, I only have double prime coated 8 doors and nothing else.
I also noted that due to water based primer, a coating on one side of the door left for a couple of hours to dry off gives rise to a slight bow in a narrow door 300mmx800mm. You have to look for it, but its there. Similar to the effect of spraying a plywood panel one side only.
If you are used to solid timber construction you will be familiar with the effect.
Its easily fixed by a balancing coat of spray if it needs it. But on 2 doors its less than .5 mm over the length of the stile, so will be asily corrected.
So after all that I've decided to go back to PC primer with a solvent base for speed of drying and finishing.
Just prepped the sprayed doors for a recoat of primer with the new pre cat mdf primer.
Sanding the old primer was ok , but running the sand paper over the old sanded material dust around the panel seemed to gather up the old dust into clogging material that filled the sand paper.
It seemed that the coat was not fully cured and hardened, so that the sandpaper could cut it into dust. This happened anywhere that the dust could gather, and be re sanded over again.
As around the panel where the dust could not escape. Along the stiles where the dust could fall off there was no problem. It sanded smooth and left a good surface along the edge, where it was important. Normally the mdf routed edge can be a problem, but it was as good as sanding sealer or better.
The intended primer to go on top of this is an ISF coating that I will post pics later. Its a UK manufactured finish, but luckily my local suppleir for all my woodwork materials is a stockist.
As promised the intended isf coating and suitable pre cat thinner.
Proper thinner always ensures that you are mixing the best materials. I know some who opt for standard thinner, as its cheaper. Its cheaper because its gunwash, and only suitable for cleaning up the equipment after your spray job. There is a marked difference between el cheapo thinners and top quality spray thinning solvent. Dont be tempted with the crap as you will run into all sorts of problems.
Good thing about the local supplier with ISF coatings is that they can mix topcoat of any Ral colour for you.
As you can see from the door edges the first primer has peformed ok for the top coat now as it is. But OCD says i need to put the new precat primer on as well.
Back with the spraying. I went with the ISF pre cat finish after the undercoat. I thought the under coat primer was good...the topcoat finish was superb. Its the same as I used years ago, but way better now. It flows from the gun great is thinned to 10% with pre cat thinner, which I upped to 15+%. Best product I've used in many, many years.
I had to build a make shift tent in my work shop to protect the rest of the workshop . I sprayed a beetle yellow ten years ago without any tent, and everything was destroyed. So once was enough. I just have the finish side to spray 2-3 coats on, and its job done.
Spraying can be a hit and miss affair if you dont have experience with it. I used a standard cheap spray gun from Aldi/Lidl, purely because I wont invest heavily into spray guns as I rarely spray much now except my own classic cars. Whats the point in spending 100's for a seldom used piece of kit.
Secret to a good operating spray gun is cleanliness. It makes a massive difference. Spraying a drop of thinner through the gun between pot fills , wont do the job. If I leave the workshop for an hour, I empty and clean the gun, and refill in an hour. When i say clean, I strip the gun down and clean every part, spotless.
Especially the little filter at the base of the pot in the top of the gun. Its a fine filter and gets clogged eventually after a bit of use.
And dont use gun wash el cheapo thinner, and expect a top class finish. It wont happen, gun wash is a cheap solvent for cleaning equipment, its not for a fish product.
PC finishes require pc thinners, and you end up with the proper mix and a good job.
Settings for the gun were between 45-60 psi with a jet of 1.5 for the jet, for the top coat finish. At these settings the paint flowed very well with a 4" wide fan setting, and any over spray was like talcum powder on any doors 8@ away from the spray area, and wiped of with your hand no problem.
The pre cat melamine primer through the same gun with the same setting left a gritty over spray on the same surface 8' away that needed to be sanded of with light pressure on 320 grit paper. This probably could have been lessened if i increased the thinner amount. But I'm happy enough with the result and ended up with a clean workshop and no spray everywhere.
Almost done now. Doors all hung into the cabinets and handles fitted. Small trimming parts fitted around the kitchen. Drawer fronts fitted, so nearly at the end of this project. Final piece to do is to make and spray the narrow drawer front, one piece of ceiling trim , and the last piece of skirting as well as the corner unit carousal.. Oh, and change the surface mounted plug near the cooker to a slimline one instead.And the last of the vinyl splash back tiles.
All in all I am happy enough with the outcome, and cost
kadman wrote: ↑Tue Jan 31, 2023 7:48 pm
Almost done now. Doors all hung into the cabinets and handles fitted. Small trimming parts fitted around the kitchen. Drawer fronts fitted, so nearly at the end of this project. Final piece to do is to make and spray the narrow drawer front, one piece of ceiling trim , and the last piece of skirting as well as the corner unit carousal.. Oh, and change the surface mounted plug near the cooker to a slimline one instead.And the last of the vinyl splash back tiles.
All in all I am happy enough with the outcome, and cost
You've surely earned enough brownie points with this project to be allowed to bring home another vintage wreck for restoration?
Del.Monte wrote: ↑Wed Feb 01, 2023 8:50 am
You've surely earned enough brownie points with this project to be allowed to bring home another vintage wreck for restoration?
Thats brilliant, I'm gonna frame this post....and blame Gubu members for the next old VW
, but he has a gentler disposition 
