The great workshop bake-off (paint that is)

I have recently been attempting to paint my vertical mill engine.

I have chosen rust-oleum black BBQ paint based on reviews.

However, things have not gone as well as they might.

I suspect that one reason is that I was painting them initially in a damp workshop at a low temperature. Only later did I read the instructions that said, 'not below 10 degrees'.

The symptoms are two-fold. Firstly, the paint seems to chip off with a strong glare and secondly, the parts remain tacky (sticking to worktop surfaces, paper and the like) over a week after being painted.

With a later batch, I kept them and the paint inside and had the shed heater on for an hour or so before painting (so only a bit under 10 degrees, but paint and parts at 18 - 20) and that seems to have gone better.

It's been suggested that sometimes these paints need to be baked before they set properly. I'm up for that and have gained permission from SWMBO to do some cooking tomorrow. I should note that this paint does not appear to need baking either from the website or reviews, but may be worth a try.

But at what temperature and for how long?

The largest pieces are the flyhweel (2kg) and crankcase (3.3kg).

I look forward to your advice!

Iain

My wife has a lot of experience at baking things black. She says that temperature is less important than time and best to wait until the smell of burning gets to another room...
She also has experience at burning-out kitchens with chip-pan fires...

More seriously I recall wood-burner cement is 'fired' for completion at a slow progressive heat increase but the chimney spray paints don't need it but have a longer curing time.

Get shed properly warm before further attempts

pgk

Phoenix Precision Paints do a Higher temp paint in their range of Cherry Paints maybe be a little more expensive, haven't used my tin yet but have used their normal temp black and it gives a good finish. They recommended it for a loco smoke box.

David

I should add that it does not need baking to cure it and it is recommended that you paint below 10 degrees C

David

You don't mention any cleaning or degreasing before painting, you should at least wipe the parts down with a solvent first to remove any traces of oil from the surface.

Cold metal in the workshop will be the ideal place for warm moist air from your breath to condense onto and paint does not take too well to a steamed up damp surface.

I always bring any paint I intend to use into the house the night before at this time of year and more often than not the parts too. Warm paint is thinner so will come out of the can in finer droplets and the combination of warm paint and metal will allow the paint to gas off faster and flow out better. Once they are touch dry they come back inside to sit near a radiator overnight.

I've not used that particular one but the Thermacure I usually use on exhausts and flame lickers etc does need backing to fully cure but the VHT colours don't

As a matter of interest, when I was in a fellow club members workshop in his house, spare double bedroom, I saw a model aircraft fuselage, nose down on floor and tail near ceiling, it was that big. I asked him how he got such a wonderful paint finish on it, dead smooth, looked like it was plastic. He said he warms the tin of paint and applies it hot so it runs, eliminating brush marks and leaves an even coating.

Put the job in the oven with the turkey !

Both results should be interesting. !

Many years ago, I recall using standard spray paint on a job, put it in the gas oven for a short time, no idea how long, low heat ,and the result was good. Worth a try.

Painting in the cold is nor recommended and if it doesnt cure in a week, its best removed and done on a warmer ,dryer day.

Even after 40 years, i still try my luck, but getting good at stripping paint now

if you look at this link it gives some information about painting with Phoenix Paints and temperature, of course it may not apply to other makes, I have been doing some with both a brush and an airbrush in an unheated garage with no problems. Parts were placed in garage before hand and paint taken out at time of application.

https://www.phoenix-paints.co.uk/application-of-precision-paints-and-temperature

David

This is curious. Barbeque paint is ideal for blacking the inside of telescopes as it doesn't reflect infra-red light, unlike ordinary matt black paint. I have sprayed the inside of a 12" diameter tube with it, but I'm not sure if it was Rustoleum or not (a good chance it was).

I recall that a coat was dry very quickly, although taking a bit longer in the middle of the tube, but under an hour.

I once had problems with a can of paint that wouldn't set after weeks; the manufacturers were at a loss to say what the issue was.

Neil

Thanks for all the responses.. I ended up baking at 120 C for about 40 minutes after a gentle warm up fro 15 mins at 60 degrees.

Don't ask me why I picked these numbers, there wasn't much science behind it. I thought that over 100 C was needed but felt it would be better with a more gradual heat up than just sticking it on at 120 C to start with.

The results? Well, in general I would say successful. It's all murky and subjective of course, but the paint seems much more stable, though it is a bit prone to chipping / scraping on the sharp(ish) edges.

On the other side, as I handle the pieces, I find my fingers getting dirty (even after cleaning the pieces with a damp cloth), so I'm not sure it's entirely successful.

In short - a success, but certainly the better approach is to start in a warm place!

Iain

I had this problem with a reflective opto sensor, painting a mark on a pulley. Blackboard paint worked, but a slight film of oil seemed to go back to not working. Quick wipe with white spirit sorted it for another few weeks.

Some paints intended for hot work will not cure at all, at ordinary temperatures, so it may be wise to carry out a little research first.

I recall once at work we wanted to paint the wooden transport-cases for certain items, black to hide their origins. The boxes were in normal grey paint with stencilled lettering. One of the group obligingly bought a tin of black paint from a local ironmongers, and we applied it; all over the box, not just the sign-writing.

People were still getting black marks on their hands from it three years later, though by then the surface was more powdery than sticky.

The tin was clearly marked "stove paint" with a note on its purpose!

I’ve had good results with Paragon paints recently, in a fairly damp and cold shed environment, and it curing nicely it seems, and fairly quickly.

Also the nicest surprise was the amount I needed, I bought 2.5 litres and must have used 0.5 litres for two coats on my horizontal mill. Enough to do 4 more. If only I’d known that when I bought the stuff.

Steve

I use smith & allan vehicle enamel for models & also for all my alloy castings ,but I allways 2 pack etch prime everything first as paint just chips off alloy & brass if not etch primed ,it sprays, airbrushes & brush paints well & then into the rayburn cooler bottom oven overnight,& I don't need the mrs "permission" either!!.for spraying I thin with cellulose thinners. or white spirit if needed for brush painting

Edited By the artfull-codger on 29/12/2021 16:30:34