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MITRA Forum Question Details

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  • Damir PusicApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2019-03-18 10:00:33 ... Most recent comment 2019-03-19 09:21:21
    Varnishes Studio Tools and Tips Health and Safety

    ​Hello MITRA,

    How long it takes for turpentine to evaporate from a freshly applied layer of dammar varnish over an oil painting with dimensions 80X60 cm?

    I plan to invest in local exhaust ventilation (LEV), so it would filtrate varnish vapor. In this process I would varnish painting inside a LEV hood. I don't konw how long to keep it inside.

    Kind regards,

    Damir P.

Answers and Comments

  • EditDeleteModerator Answer

    ​With old-fashined tree exudate gum varnishes like damar and mastic, the time required to achieve a tack-free coating can be irregular, depending on factors like ambient humidity. Many artists simply will not varnish on a rainy day at all, to avoid risking long-term tackiness. In my studio, I recall that a thin coat of factory-made damar dried to an acceptable, tack-free hardness in 2-3 days when humidity was low; homemade varnish would take a day or two longer. Drying rates were not uniform, though- sometimes a picture would remain tacky longer than was convenient, and I learned not to be in a hurry where damar was concerned. Years ago, I adopted acrylic solution varnish and found that drying times were more regular and shorter, and that removal (when necessary) was much easier, with less risky solvents. 

    Matthew Kinsey, Utrecht Art Supplies
    2019-03-18 15:47:53
  • EditDeleteModerator Answer

    There are far too many variables here for me to be able to answer this question. First evaporation rates are given as ratios compared to diethyl ether. Oil of turpentine is listed as 170.

    This does not tell us much but there are many more important factors here.  For instance, what cut is the varnish (how much turp to how much resin)? How thickly was it applied? What is the temperature in the space? What is the RH? If this is going to be in a hood, what is the airflow? What is the affinity of dammar to hold turpentine? Finally, I do not use dammar so I can’t speak even empirically on this. Perhaps someone else will take a stab at giving you a time range despite the difficulty of being very precise given the above.

    Brian Baade
    2019-03-18 15:48:26
  • EditDeleteModerator Answer

    ​Matthew, it looks like we cross posted. Thanks for adding some practical info here.

    Brian Baade
    2019-03-18 15:49:38
  • ApproveRejectUn-ApproveUser Comment

    ​Matthew, 2-3 days seems too expensive to let LEV working, maybe it's possible to speed it up by changing the airflow as Brian implicated.

    However, now I know the answer is laborious, maybe impossible to grasp it mathematically. I'll try to get insight to in situ data.

    Damir P

    2019-03-19 09:21:21

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