Dammar varnish makers, have you ever tried...

[Einion]

...a blend with mastic?

Einion

[rroberts]

Why do you ask?
I always find your technical posts informative, so you have piqued my curiosity.

I haven't tried a blend, mostly because I haven't felt any need to do so.
Interestingly, the recipes I have that use both damar and mastic also use sun-thickened oil or stand oil. Massey varnish #10 is a combination of damar, mastic and wax varnishes.

[O'Aieghlans]

According to my reading, mastic has a tendency to bloom.

I'm not sure what mastic would add to a dammar varnish ... do you have some idea?

[turlogh]

According to my reading, mastic has a tendency to bloom.So does dammar.

I have read that some museums like a 15/85 blend of mastic/dammar as a varnish. I am not sure what properties a blend would have to make it superior to straight dammar, so it isn't very helpful that I ran across this "fact" somewhere.

[Robman]

According to my reading, mastic has a tendency to bloom.

I'm not sure what mastic would add to a dammar varnish ... do you have some idea?

As Turlogh already said, so does dammar. I've read that it's moisture trapped between the painting and the varnish that leads to blooming. But this is pure book knowledge. I haven't actually seen this for myself. Can anybody direct us to images of paintings in which blooming occured?

[Robman]

Let's hear it for google. Yeah, I think I can see how blooming could be interpreted as a bad thing.

http://www.art-conservation.org/Glos_paint/Blooming_Varnish/gloss_det_paint.htm

[Robman]

Finally, I think this thread from Cennini is quite educational on the matter. For those unfamiliar with the forums at studioproducts, the beginning of the threads are at the bottom of the page.

http://www.studioproducts.com/forums/viewtopic.php?t=6179&highlight=blooming&sid=3e9ef4642ce936e6f4553f5fa954c18f

DeLac mentioned waxes and mineral spirits as a pollutant in dammar, which I already knew, but the presence of water was a new one to me. The water in the dammar would certainly contribute to blooming. However, Rob Howard's observation that present day homes are warmer and drier than those of our great grandfathers certainly explains the lack of examples of modern day blooming. It would certainly explain why I've never witnessed blooming in any of my own paintings, and I have to confess that I've rarely taken the care to make sure that the surfaces of my paintings are 100% free of moisture before applying the varnish.

[Robman]

So anyway, what's the advantage of a mastic/dammar mixture?

[Rosic]

Some interesting info here...
thanks for the link Robman.

[Mark Diederichsen]

...a blend with mastic?

Don't they call that a "museum varnish"?

Add just a little mastic to make it less glossy, but not totally matte.

Might be easier to remove too because mastic is softer, but I'm not possitive about that. Damar, by itself, is difficult to remove if left on too many decades.

I'm talking about a final varnish because I'm unfamiliar with it as a medium.

[Einion]

Don't they call that a "museum varnish"?Yep.

Einion

[O'Aieghlans]

According to Mayer's "Artist's Handbook", there is no truly nonblooming surface. He says that mastic varnish has a greater tendency to bloom than dammar varnish. The present of mastic in megilp (linseed oil and mastic) medium leads him to say that mastic should not be used by anyone who is concerned about the longevity of his/her paintings. In other words, it's no good.

So while adding mastic to the dammar might impart some interesting if not pleasurable qualities, as it does in megilp medium per Mayer, I still am not sure what it would add to the varnish in the long run.

[Einion]

I have read that some museums like a 15/85 blend of mastic/dammar as a varnish. I am not sure what properties a blend would have to make it superior to straight dammar, so it isn't very helpful that I ran across this "fact" somewhere.In the past the varnishes that used both would have something like the reverse proportions.

The reason I mentioned this is that a blend appears to age better than either resin used alone. However it's much more likely that a simple addition of a UV-inhibitor to standard dammar varnish, if one insists on using a natural-resin varnish, would be a better bet if you can locate a source. In addition to protecting the dammar itself it would give added protection to the painting.

Don't they call that a "museum varnish"? Checking my references I should have been a little more precise, it's one version (others used all sorts of other ingredients).

I am also only referring to varnish in the true sense of the word above.

Incidentally if you read up on the issue you'll see mentions that mastic was commonly adulterated with dammar after the latter became available because it was far cheaper. It's interesting to speculate that this might account for the superior condition of some painting executed with 'mastic' mediums!

Einion

[Einion]

I need to address the blooming thing here. In common parlance it might be different but clouding (which most of you are referring to) and blooming are two distinct phenomena. Clouding isn't uncommon with moisture problems around the time of varnish application - any varnish might be affected - blooming on the other hand is something that aged varnish layers display for reasons that are unclear.

Einion