Why the colour miss match

[ArAKern]

I had a bad run in this area and in attempting to remove it, cut through to the primer. Rather the repaint the whole quarter (in hindsight probably the better solution) I just masked up a small area

The only difference was the temperature of the day much colder, but you can clearly see the square. So why the colour miss match?

 

[m_c]

It's white.
Due to the lack of pigment with white paint (and other pale colours to some extent), the final colour depends on pretty much every part of the process, but in short, it's likely different thicknesses in the final coat so the base coat/primer is shining through.

I once had to fix somebodies repair, as they thought you should use white primer with white paint.
Looked OK until he put the top coat on, at which point the filler became visible

 

[ArAKern]

I think the camera flash made it look white it's actually a direct to gloss cream.

It was re-painted with the same paint, thinner and hardener as the rest. The rub through was only a small area in the middle of the patch and some scuff marks from the carborundum block.

I would have expected the extra layers to make it look darker rather than lighter??

 

[slim_boy_fat]

as they thought you should use white primer with white paint.

As a novice [who hates painting anyway ] I'd have probably made the exact same mistake.

 

[500e]

Would not have masked gives a hard edge difficult to polish out

 

[slim_boy_fat]

Would not have masked gives a hard edge difficult to polish out

I suspect so, unless something like this was used? CLICKY No idea if that stuff is thinner in cross section.

 

[MetalMonkey]

Would not have masked gives a hard edge difficult to polish out

+1

You are always going to have hard lines where it was masked, even if you spray and try and blend it in, you will probably see a patch that is different in colour.
To do it properly you will need to use blending techniques, possible blending/fade thinners - ideally have a sufficient sized repair area to fade the blend into, and preferably a join in an area where it is hard to spot (e.g. across a door pillar) rather than bang in the middle of a panel.

It is a real art form to blend, and some colours are very difficult to do.
As an amateur, it isn't a skill I've mastered, I've had very mixed results and frankly I find it way easier and quicker to just respray the panel and hide the join on a panel gap or trim line.

 

[500e]

Did it for years @MetalMonkey just pointing out a masked edge will be nigh impossible to lose
Had two paint shops.
You could blend across a panel to help loose a slight mismatch in colour, or paint whole panel & then blend next panel to lose the change in shade, the painters we had would tint to help loose colour variations, none of these machines to help in those days

 

[500e]

@slim_boy_fat
Yes.it is thinner we use 3m blue fine line where we join 2 colours it is a different material to standard tape.
We don't do much painting now as in different business usually only 3 colours white semi mat black and orange, occasionally yellow

 

[ArAKern]

I appreciate doing a blend or painting the whole panel would have avoided a hard edge. But that is not the question. Why is there a colour difference?

The paint was from the same tin as the whole of the topside, same can of thinners, same can of harder. same gun.

apart from the day being colder I don't understand how there is a colour mismatch???

 

[Pigeon_Droppings2]

The paint was from the same tin as the whole of the topside

Could it be the mixing of the tin was slightly different...producing a different "blended" colour?

 

[MetalMonkey]

I appreciate doing a blend or painting the whole panel would have avoided a hard edge. But that is not the question. Why is there a colour difference?

The paint was from the same tin as the whole of the topside, same can of thinners, same can of harder. same gun.

apart from the day being colder I don't understand how there is a colour mismatch???

I'd say it would be more surprising if there wasn't a colour mismatch!

The exact same paint mix can even look a different colour if you spray the panel at a different angle, or from a different distance, or a dozen other variables. The application, texture and thickness all make a subtle difference.
Even very precise mixing by weight won't give exactly the same shade, so every mix is slightly different - that is why colour matching and blending is an art-form.

You would never spot it on two different panels, even next to each other, but any sort of masking line will show up like a sore thumb, I'm afraid that is just part and parcel of painting cars.
I reckon if you had masked down that vertical seam, and hid the transition there, you might have got away with it

 

[500e]

Also if paint ia not mixed you can get v small amounts of pigment in tin seams that can throw shade

 

[ArAKern]

I'd say it would be more surprising if there wasn't a colour mismatch!

The exact same paint mix can even look a different colour if you spray the panel at a different angle, or from a different distance, or a dozen other variables. The application, texture and thickness all make a subtle difference.
Even very precise mixing by weight won't give exactly the same shade, so every mix is slightly different - that is why colour matching and blending is an art-form.

You would never spot it on two different panels, even next to each other, but any sort of masking line will show up like a sore thumb, I'm afraid that is just part and parcel of painting cars.
I reckon if you had masked down that vertical seam, and hid the transition there, you might have got away with it

Many thanks for the info. I did think about painting the whole quarter but is was such a small rub through. Well lesson learnt. There are some other areas I did the same but that one showed the worst.

 

[Misterg]

Why is there a colour difference?

Whites and greys are the worst colours to try and match. I'm not a painter, but I used to work in a factory making sunglass lenses (amongst other things) - people generally want both lenses of their sunglasses to look the same, even if they were made months, or even years apart, so we had to try and contol the colour. Greys were by far the most difficult.

People have come up with various ways to describe and quantify colours and our perception of them (colour spaces). Without getting bogged down in details, imagine that all the available 'pure' colours are arranged around the edge of a circle. If you walked around the very edge of the circle, you'd cycle through bright red, bright yellow, bright green, etc. Move inside the circle a bit, and you'd see the same colours as you went around, but less vivid and pure, and so-on to the centre of the circle. At the very centre of the circle, no matter which way you faced, it would be pure white* - there's no discernable colour. The human eye is so sensitive, though, that as soon as you move away from that centre it can see to the nearest point on the circle and it perceives that colour, so the white (or grey) has a 'cast'. The nearer the middle you're aiming for, the smaller the difference that will create a cast. If you think you're right in the middle, but there are slight errors in your position, you could end up seeing any colour going. Your position in the circle corresponds to the detail of the paint pigment mix, spraying conditions, drying conditions, etc. The human eye is incredibly good (like unbelievably good) at spotting colour casts in a neutral base. It's easier to match things if you create a deliberate cast towards a certain colour.

*Grey, actually - As an aside, the eye is crap at gauging brightness. I went to a presentation on colorimetry once, and the first thing the guy did was hold up a card and ask the audience what colour it was. Everyone agreed it was white. A while later, he held up another card, brighter than the first, and asked what colour it was - everone realised that they had been duped, and that *this* was the white card, and the other one must have been grey. He did that three more times. At the end of the presentation, he laid out all 5 cards. The last one was just a sheet of copier paper; the first one was dark grey.