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Old 01-11-2019, 02:01 PM
Richard P Richard P is offline
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St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Hi all,

Just to let you know that Jackson's website are now selling these 3 new oil ranges..

Must tell myself.. I DO NOT NEED ANY MORE PAINT..



Richard
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Old 01-11-2019, 02:05 PM
Richard P Richard P is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

The St Petersburg Master Class Oils range does have PY32 Strontium Yellow for those that are interested.
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Old 01-11-2019, 03:28 PM
RomanB RomanB is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by Richard P
The St Petersburg Master Class Oils range does have PY32 Strontium Yellow for those that are interested.

The pigment is so nice and delicate. I have some of it in raw form. Sadly, it isn't very permanent.
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Old 01-11-2019, 03:45 PM
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Delofasht Delofasht is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by RomanB
The pigment is so nice and delicate. I have some of it in raw form. Sadly, it isn't very permanent.

Where did you hear that PY 32 not very permanent? Several manufacturers list it as completely lightfast (with possible minimal shifting toward green).
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Old 01-11-2019, 03:54 PM
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savras savras is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by Delofasht
Where did you hear that PY 32 not very permanent? Several manufacturers list it as completely lightfast (with possible minimal shifting toward green).
Which is very definition of being impermanent.

From ArtIsCreation:

may turn greenish due to the partial conversion to chromium oxide

source
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Old 01-11-2019, 04:17 PM
RomanB RomanB is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by Delofasht
Where did you hear that PY 32 not very permanent? Several manufacturers list it as completely lightfast (with possible minimal shifting toward green).

From the classic treatise "Chemistry and Technology of Pigments" by Belen'kiy & Riskin.
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Old 01-13-2019, 01:37 AM
bhindi bhindi is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by RomanB
The pigment is so nice and delicate. I have some of it in raw form.
Do you mean you have strontium chromate powder? India produces a lot of that pigment but exports it for use in commercial paints. I have a sample packet with me but the supplier told me it was "chemical grade". I never ground it because I thought the pigment size may be too large for oil paint use. Can you share any specs for what you have and if you were able to grind them into usable oil paints?
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Old 01-13-2019, 02:08 AM
RomanB RomanB is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by bhindi
Do you mean you have strontium chromate powder? India produces a lot of that pigment but exports it for use in commercial paints. I have a sample packet with me but the supplier told me it was "chemical grade". I never ground it because I thought the pigment size may be too large for oil paint use. Can you share any specs for what you have and if you were able to grind them into usable oil paints?

It is sold here as artist’s pigment. It mixes well with linseed oil using a glass muller and a glass slab. Precautions should be taken since the pigment is not harmless, so proper ventilation and personal protective equipment are necessary, and waste should be treated as containing this substance if it’s regulated in your country.
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Old 01-12-2019, 12:03 AM
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Delofasht Delofasht is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Guess you guys did not read the pigment manufacturers information on the pigment then... the warning about possibility of it turning green is an effect caused by certain chemical exposure. It is still considered lightfast because very specific sets of variables are required to cause the color to change.

Want to know another yellow considered highly lightfast, but in fact will darken in some media or fade when exposed to excessive light? PY 35, happens when the pigment becomes exposed by remove of the binder through the use of solvents commonly used in oil painting. Nothing is permanent or lightfast if the conditions are not right for it, I just suggest we stop trying to make everything out to be less than what it is.

From a chemical analysis point of view, PY 32 seems to be a solid color, though it’s most common use seems to be in industrial coatings which often get exposed to various highly unfavorable conditions (radiation, corrosive and caustic chemicals, and many others).
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Old 01-12-2019, 10:10 AM
RomanB RomanB is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by Delofasht
Guess you guys did not read the pigment manufacturers information on the pigment then... the warning about possibility of it turning green is an effect caused by certain chemical exposure. It is still considered lightfast because very specific sets of variables are required to cause the color to change.

There is a Russian State Standard GOST 11826-77 for artist's oil paints, a document similar to ISO and ASTM standards. It states that Strontium Yellow oil paint is marginally lightfast and changes color significantly after 5 months of exposure to direct sunlight, from May to September. Manufacturers could make it better than this standard demands, but no means are able to make the paint completely lightfast.
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Old 01-12-2019, 10:58 AM
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Roman, it appears that your document is over 40 years old... pigment technologies have improved quite a bit since then and the pigment that was tested for that document may well have been of a poor quality in itself. These issues arise in ASTM and ISO standards as well, except that the standards are revised a bit more often usually.

Further exploration has many manufacturers now days claiming it at a very high lightfastness rating (usually 8 on the BWS).
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Old 01-12-2019, 11:18 AM
RomanB RomanB is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by Delofasht
Roman, it appears that your document is over 40 years old...

The Standard has three revisions and the last one is not so old, but I doubt that pigment's properties changed significantly. Other Russian paint manufacturers also mark it as marginally lightfast, with one *. Gamma, Podol'sk. Maybe there is a method to improve its lightfastness, like adding Tinuvin light stabiliser, I don't know if they use it.
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Old 01-12-2019, 12:26 AM
bhindi bhindi is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

@Richard P - Thanks for the info. Great that Jackson's is offering Masterclass.

I use PY32 and have not noticed any color shift in 2 years. It is a very nice lemony yellow.
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Old 01-12-2019, 10:36 AM
bhindi bhindi is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Is this the row of information you are referring to?
There are 3 columns with temperature information. How do you read this table?
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Old 01-12-2019, 10:59 AM
RomanB RomanB is offline
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Re: St Petersburg Master Class Oils, Langridge, and Maimeri Puro

Quote:
Originally Posted by bhindi
Is this the row of information you are referring to?
There are 3 columns with temperature information. How do you read this table?

Yes. Columns are:

| Paint's name | Product classification code | Lightfastness or yellowing for white paints | Maximal particle size, in micrometers | Shear stress limit at 20 ± 2 °C, in Pa*10^-2 | Ropiness at 20 ± 2 °C, not more than, in millimetres | Drying time at 20 ± 2 °C, in days to degrees of drying 1 and 5, not more than | Adhesion, not less than, in mm |

It has one X in lightfastness column, later it is specified that paints with one X are marginally lightfast and methods of determining this quality are described.
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