The truth about POPPY OIL

As too much people think; POPPY Oil doesn't make more cracks than Linseed Oil :

Cracking is a result of drying. Oil dry in 3 stage ;

  1. Oil absorb oxygen to extend its volume (12 or 13 per cent of its weight for linseed oil, more than Poppy), and becoming solid and denser on the surface coat.

  2. Underlying coats, more flexible, continue to absorb oxygen and in the same time volatiles yields products are liberated by channel created in the surface coat (That’s why a second coat, on a first more fat makes “embuts” by aspiration)

  3. Oxidation and polymerisation; 

Oil = glycerides (that is compound from glycerin and fatty acids) + fatty acids free

OIL

Composition in Fatty acids

 

Saturés

Oleic

Linoleic

Linolenic

Poppyseed

24

0

76

0

Linseed

10

22

13

55


Poppy oil contains linoleic acid, and Linseed oil contains linolenic acid mainly.
During drying, the oil is under 2 phenomenons : polymerisation and oxidation, or absorption of oxygen from the air.
One of the consequence of oxidation is yellowing for linseed oil
The other consequence, in long-term, is crackeling;
Oil absorbs oxygen to extend its volume , and then becoming converted into a mixture of substance which name is “linoxine”. Linoxine is solid and denser than the original oil. In consequence of this expansion, a layer of raw oil spread upon glass becomes wrinkled during the drying and oxidizing process.

In the last stage, the oil continues to absorb oxygen very slowly, during a very long time. The substances yields come out of the paint, the volume go down and crack break out.
Many substances favour the absorption of oxygen (manganese dioxide, borate,..). That’s why siccatives are not recommended.
This contraction is occured by oxidation, but also by polymerisation, depending on light, pigments, additives, temperature, and so more
.

So, the most important for your paint, is ;
No siccatives
Aplly varnish layer after one year (to reduce absorption of light)
No too much light, no too much temperature, no too much humidity

The difference in this process of drying, between Linseed oil and Poppy oil, is the time for the first layer to dry, and yields products. More oil dry quickly, more contraction, and cracking hazards are important.

However, in practice, the changes which occur during this oxidation are complex and ill-understood.
That’s why we make test for more than 140 years, and we ever prove that Poppy oil is better, for no wrinkling, but also for consistency, brightness, application, and of course non yellowing.

It is nearly free from taste and smell, and it permits to obtain pure dabs with possibilities to touch the work up easier in superposing without waiting the complete drying of the lower coat.

Everyone is free to choose !

 

 



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