Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: callingtotheoutside on 26/07/2009 10:58:21
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I was just wondering if during production paint is white and they add different colours once its finished, or if to get white paint you have to add the white, it could start a yucky brown or something for all i know?
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I was just wondering if during production paint is white and they add different colours once its finished, or if to get white paint you have to add the white, it could start a yucky brown or something for all i know?
Your question is not very clear to me: you want to know how white is made or how are made the others colours? Anyway, to make the others colours they don't start from white, they start from the specific colour, unless you want the clear version of that colour; to get rose, for example, you add white to the (pure) red.
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I was just wondering if during production paint is white and they add different colours once its finished, or if to get white paint you have to add the white, it could start a yucky brown or something for all i know?
Most sorts of paint can be described as a mixture of two basic elements: The pigment (the stuff that gives the paint the color) and the base (the main 'bulk' of the paint that forms the substrate or structural suspention vehicle for the color/pigment).
Wall/house paint, at least latex based paints, are usually made out of a base and a tint or pigment. While you can still buy pre tinted, pre mixed paints at the store, if you go into Home Depot, Lowes, or wherever, other than a few common colors (Blacks, whites and a few others notwithstanding specialty paints), most latex wall paint is now sold as a two part mixture: The 'Tint base' and the tint/pigment. there are usually cans of variously colored pigments that can be mixed by computer directed proportions to yield a nominally infinite array of custom colors. The tint/pigment is in turn mixed with the larger can of base to provide the ready-to-use paint of a given color. Specifically to your question, the 'tint base' is essentially the uncolored paint, and there is usually a range of cans labeled 'tint base 1', 'tint base 2', 'tint base 3', etc... Their exact composition and properties depending on your final desired color..... they vary somewhat, but they all pretty much look like a weak off white (IIRC). 'White' paint is a base with a bright white pigment, probobly titanium dioxide, added.
If you want to get into the same question for artists paints, the answers are somewhat different.
For acrylic paints, the paint is a mix of finely ground pigment with acrylic medium or gel (it is a water disolved monomer that becomes a stable bound and non-soluble polymer as the water dries from the medium... a one way chemical reaction). Unpigmented gel has uses of its own including providing a clear sealing layer to a painting and also can be mixed with pigments supplied by the artist to make custom, home made paint. In wet, unapplied form, the gel/medium is translucent and cloudy. It dries and afterwards remains clear.... although yellowing can result with age.
Oil paints are exactly that: Oil with pigment mixed in. The oils include Linseed, Walnut, poppy seed, and many others... all with their own atributes and characteristics. Appearance is typically mostly clear to pale to medium yelllow... mostly clear but sometimes a bit cloudy.
Walter color paint without pigment would look like a granular whitish powder (Dry gum arabic and sugar). Alternately it could be a whitish block or a cloudy paste.
There are still other kinds of paint that have their own distinct qualities and appearances when formulated 'without pigment'.
I may have kindof overkilled the question, but the materials aspect of art is something I am kindof interested in. [:)]
diogenesNY
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What can i say diogenesNY but wow, thank you vey much, you answered my question and some [;)]
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White is a solid pigment, so while it doesn't seem to cover other colours very well, All this extra material, as well as the extended process, translates into higher cost.
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Before we go through the question, let us take a look at a few facts about colour. Basically the choice of colours varies from one individual to other. There is a whole subject of study on colour and the human psychology and hence a small study on the topic shall be worth a while.
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Your paint base can, for the vast majority of the colours you can buy in stores, be made from one of two formulations. Both are an identical blend of vinyl acetates, that are the binder, and all the other ingredients that get added to it to give weather resistance, water resistance, gelling ability and such, creating the base compound. Then they mix in filler materials, which are there to give bulk and provide the gap filling and levelling ability. For those intended to be tinted dark colours, the so called deep tint base, this is finely powdered chalk, added along with magnesium oxide powder, so as to allow a dark colour tint to predominate the finish colour.
For those that are destined for light bright tint there is a lot of titanium dioxide added, as a white reflective part, along with the other chalk and magnesium oxides, so that light is reflected off it well, giving you the base of white PVA paint, which is the base coat that your lighter colours are tinted with.
In the store, or at the factory, if they are making bulk batches of paint, or a single can in the store, you get a colour pack added to the base, and then mixed to disperse it through the bulk liquid. The colours are generally composed of large amounts of the colour pigments, organic molecules in the most part, finely ground, and mixed with the acetate base and stabiliser that is the base without the filler, and deeply concentrated to a consistent particle density, and then packaged in smaller paint tins, for retail mix typically 1l plastic tubs. Then at the store level you have your paint swatches, which are all coded as to the colour, and that colour number is used by the mixing computer (almost invariably computer controlled these days, rare to find a shop with a manual mixmaster and a recipe book telling you the info for each base, quantity and colours to add to get the desired colour) to drive an automated dispenser, which takes a carousel of the various colours, all regularly stirred so the pigments do not settle out. Then it rotates the carousel to the desired colour, and activates a precision pump that dispenses the volume of pigment needed per colour, from 0.1ml to 200ml which is dropped direct into the opened can underneath. After the dispensing the can is sealed again, and placed in a shaker to blend the individual colours into a single homogenous paint in the can, and also mix the settled pigments in the can as well.
Your colour will be made from up to 10 different volumes of pigment, often containing black, brown and green, even for the predominantly blue colours, just to shift the colour to the right shade to match the colour samples.The 20 odd mix colours are also added to the oil based paints, where the PVA base disperses in the oil base, and still provides a similar colour, though your colour there will have a different formulation, adjusted for the different base, to get a very close colour match irrespective of base component. There is slight variability between batches, which is why you get told by professional painters to order all the colour you need as a single batch, or at least paint a room with the same batch, so as to not have slight colour shifts in the pastel tints. And yes, one of the colour tints is actually near pure titanium dioxide, added to make the brighter shades of light pastel paints, adding extra reflection to the paint.
An anecdote is the one new complex decided on the colour they wanted to use outside, which resulted in them needing to use 1.2l of the phthalo blue tint per 25l bucket, so they actually got 26l per bucket of paint. They ordered so much that the paint mixer shop, who were supplying them with the paint on demand, was not using the 1l tubs of phthalo blue to mix, instead receiving it in 200l drums, and using a drum pump and a bucket, to move it to next to the mixmaster, and then pouring in 2l at a time, while the machine was dispensing. They never got the blue stains off that area of floor. I wanted a 5l paint mix, so simply grabbed one of the older staff who knew how to use the manual mixmaster and the recipe book, as I had already gotten the 5l can of deep tint base off the shelf, I knew the base needed. They had a pallet of 25l buckets ready to go out, and another under construction, with 10 stacked there for the rest of the week. They were getting 20 pallets a week of just the one base for this order, and it took 3 months to complete.
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It seems unlikely that the OP is going to return to a decade-old post.
Just in case they do- until you add the pigment, you don't have paint. So the question makes no sense.
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'White' paint is a base with a bright white pigment, probably titanium dioxide, added.
Before titanium dioxide, lead oxide was often used as the base. Lead is a neurotoxin, and children sometimes picked up lead from flaking paint, or even lead paint on kid's toys. Thankfully, lead paint (and leaded petrol) is now banned.
Even farther back in time, lead oxide was used in makeup.
There have also been cases where arsenic was used as a green tint...
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Yes, white lead oxide as brightener in paints, and arsenicas Sceles green, a very popular colour for wallpaper in Victorian times, which also had the unfortunate problem of outgassing arsenic vapour, and the same arsenic compounds were used to dye clothing, along with their use, as arsenic oxides, mixed with lead oxide as face powders.
Then you have, even to this day, mercury compounds that you can still buy, used as skin lightening creams. Banned in most countries, but still made and brought in all over the world.