Food safe finish for MDF

[Jeremy Brant]

I'm building a simple 3 tiered collapsible cupcake stand out of mdf for my wife. I built one a few weeks ago and didn't like the way the finish came out, so I decided it was simpler to start over rather than strip/sand and refinish. I used BIN primer, then used a new Valspar paint with 'easy spray technology' that indicated you could respray in 5 minutes. The spray worked fine, and the finish came out ok, but it never dried to a real hard surface and stuck to itself. It even stuck badly to the cloth it was wrapped in for transport, even after letting it dry for about 2 days.

I have HVLP spray equipment that I can use if necessary, but for the small project I was hoping an off-the-shelf spray can would suffice. Not that it probably matters in choosing the specific paint, but it needs to be white in either semi-gloss or gloss. Also, temperatures are starting to fall with highs in the mid-50's for the next several days. I can heat up the garage some, but would prefer to spray outdoors, as long as it is dry to the touch within an hour or so. I could bring it indoors at that point to dry further. Any recommendations for something that won't stick to itself and will harden appropriately when dry?

[sheldon pettit]

Jeremy, the drying times listed are for temps at or above 75 degrees and 50% humidity, [typical lab conditions] In actual use, look to see the minimum temp it should or can be applied at, and follow it. Low temps always slow the drying down on all normal coatings.

[Rich Engelhardt]

Just the week before last I brushed two coats of Rustoleum satin finish white, oil based, onto an exterior steel door.
The air temperature was in the low 50's.
Aside from brushing sort of poorly - a fair number of brush marks showed & there was zero flow of the material - it dried fine within a couple of hours.

We were sort of stuck between a rock and a hard place since the job was winding down (2nd last day we were there) and the steel door has a 120 day period where it needs coated, otherwise it voids the warranty.
I would have preferred to use a 100% acrylic, but, the acrylic wouldn't have cured quick enough and would have stuck to the weather stripping when the door was closed.

Plan "B", if the Rustoleum hadn't dried like it did, was to take the door down and move it inside.
Since it was an outswing door & there's no way to pull the hinge pins, we would have had to remove the hinges by unscrewing them.
The hinge screws were brass & had been factory installed. That spells trouble about 50% of the time. An impact driver helps a lot - but - we didn't have one.

Some things to consider w/oil @ less than recommended application temperatures:
- Flow decreases to near zero. It can be made more workable by adding Penetrol - but - the Penetrol extends the drying time.
- Air flow is critical. The more the better - w/in reason.
- Don't apply it in the direct sun. That will cause it to surface dry and trap solvents.
- The sheen becomes uneven. Try to avoid using anything more than a semi gloss - satin finish if you can get away with it.
- Apply it & leave it alone. Don't even think about brushing or rolling back into it. The open time for this is decreased to seconds. (Trust me - I was moving @ Mach 10 doing the raised panels so they would look decent - where the sides of the door and the cross members intersect & you have to change brushing direction was another toughie).
- Make sure your first coat is really dry all the way and not just surface dried. I brushed a coat on a piece of scrap material & set that by the door. I tested the dryness of the scrap by digging my fingernail into it insstead of risking the finish on the door.
- Don't use a rattle can....by coincidence, we had to also touch up some metal railing we'd installed. We used a rattle can of Rustoleum for that. Same day. same conditions. The stuff in the rattle can was still tacky at the end of the day. It had to set overnight to harden. Needless to say, it looked like hell the next day. Thankfully, it ws hard enough to sand & the temperatures the next day had gone up into the low 70's and we had a good hour before the rain set in.
That mirrors my past experience with rattle cans and sub-optimal temps. They simply don't dry when the temps get under 60 or so.

- An hour dry may be pushing it. I honestly don't know exactly how long the door took to dry. I put the first coat on @ 8:30am and didn't get back to check it until somewhere around 11:30. Same with the 2nd coat. I put that on at 11:30, then got tied up with other stuff until somewhere around 2:30/3:00.

- You are 100% on your own. I can't stress this enough. If anything does go wrong, it's all on you at that point. The Mfg. won't stand behind the material since it was applied in conditions they don't recommend. Even though I did it & got away w/it, I can't recommend it.
The only way I would even suggest you try it would be if it were a last resort. I don't want to come across as a jerk here...it's just that it's one of those things that because you can do it - it doesn't mean you should do it. (Untold thousands throw back one too many, then stagger to their car and dirve home w/out killing anyone or getting stopped - that doen't by any means make it ok).

- There are some specialty coatings that are made to go on at lower temperatures. Insul-X makes a Freezer-Kote which can be applied atjust about any temperature below 40*F. It's make for walkin coolers and has USDA (food safe) approval.
My experience with similar materials is that they work as advertised - but - are very poor in appearance. Brush marks, roller stipple and spray shadows are very pronounced.
However - in a walk in cooler,,,,appearance is a very low priority.
They are also a good bit of $$ and not something you'll find on the shelf. When you do find it - you may have to buy a gallon, or more..

HTH - and BTW, if there's any possible way to avoid doing it, I'd really recommend that instead.

Edit to add - re: food safe.
There's little in the way of anything toxic these days once a paint film has dried.
There are some exceptions where a mildew resistant material or an industrial/commercial material is concerned - but - for just about anything you can buy over the counter, you should be fine.
HOWEVER - this only applies to something that isn't subject to health department regulations/requirements.
if you making something for yourself or even possibly as a gift, there's not too m uch to worry about.
If you're making them to sell to someone in the food industry, that's a whole different matter.