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Seasonal drying times

I've been giving my paintings six months drying time.  But I realized that a painting I complete now will not have the benefit of my local high July/August temperatures to cure.

I could wait a year instead, that would guarantee each painting gets the warm weather to speed drying.  But simply waiting for a length of time is not scientific, because we are all in different seasons and climates, and the materials are different in most cases.  That makes any time-based drying guidelines mere guesswork.

Is there a way to determine whether a painting is dry enough to varnish?  I know the fingernail test, but that only works for thick paint.

Comments

  • Could you not put the paintings in a warm place (near the boiler?) to make sure 6 months will be ok
    PaulB
  • Post it to my house and it will dry in a few days!!! @PaulB
    but seriously - my painters thet work for me have curing / drying ovens in there workshops ( for bespoke items)  - some are the size of a car, maybe they would  let you store them for a little while if you know any local at least the temp will be constant and controlled 
    PaulBjswartzart
  • SummerSummer -
    edited December 2017
    Whatever drying methods you try, I think in the end you will have to go with your gut instinct plus another two months.  Edit:  But then, I don't have time constraints.
    PaulB
  • Thanks guys, but here is what I'm after:

    I know I could speed up the drying process using heat, but that just shortens an unknown drying time to another drying time.  A curing oven may be the ultimate way to shorten a drying time, but I still don't know what that is.  As for instinct, that's what I'm trying to avoid, it's the engineer in me.

    @martinvisser Retouch varnish (as I understand) is porous to some degree, and allows a painting to cure underneath the varnish and essentially doesn't seal it.  But the instructions for retouch varnish are to make sure the painting is dry first.

    Given that there are so many variables, it will be impossible to come up with a formula indicating drying times, because of paint, solvent, climate, thickness, substrate etc.  That's why I'm asking if there is a test.  In other words, if I hand you a painting, can you tell me if it's dry, and if so, how?
  • The only thing I can think of is to take the slowest drying pigment you use when doing the painting and make a thick blob at the side of the canvas with the same medium you are using. Then keep testing this with a knife periodically. When it's fully hard all the way through then everything else should be properly dried.
    BOB73
  • @PaulB ; A "curing oven" will speed up the drying time to several weeks instead of months but you still need to test it as @Richard_P suggests. I describe a home built "oven" for @Summer in this thread:

    http://forum.drawmixpaint.com/discussion/comment/83981#Comment_83981

    I have learned since that the light should shine on the painting (front) and My concerns for UV light as mentioned were unfounded.

    PaulB
  • @PaulB ; I'd just like to mention that my gut instinct is my inner voice and my engineer--must be my age.  :)
    PaulB
  • PaulBPaulB -
    edited December 2017
    @Richard_P Yes, that's better, but it's still the fingernail test performed on a sample that must be made to simulate the worst of the thickest paint/layers/mess on the canvas.  The problem with the fingernail test is that I can make marks with my fingernail in a wood panel, so there is no painting where I can't make a mark.

    @BOB73 If I could make one part of my home warmer than the rest, then I'd live in that part.  Not a fan of snow.

    @Summer, yes, instinct is all I have too, but mine is based on only months of experience, and none of those being winter months.  But it's a chemical process, it's well understood (but not by me), and there must be a way to tell if it's complete.  Need a Chemist...
    Summer
  • Found this @PaulB

    How do you know that the oil painting is dry?

    There is a very simple test.

    Take a lint-free rag and dip it into white spirit. Pick an inconspicuous area and gently rub. If any colour shows on the rag, it requires further drying time before varnishing or framing.

    PaulB
  • @alsart, right, but that only tests if the surface layer is dry, and sounds like you just keep damaging the painting until you can no longer damage it.


  • SummerSummer -
    edited December 2017
    @PaulB

    This was written by Aires on WetCanvas some of which was mentioned earlier by you and others but I'm posting it here now because it is concise and all in one place:

    "Oil Paint dries by oxidation and that requires air being able to reach through all the layers. That is why heavy coats of paint need a full year before having a final varnish coat. If a final varnish is used too early, even when the paint feels perfectly dry, there may be problems later because the paint has not finished drying. A thinned down varnish, usually called a retouch varnish does not seal the oil paint, enough air gets through to let the paint dry completely. So the truly safe way, if using varnish, is to use a so-called retouch varnish when the paint feels dry and then wait for 6 months to a year for the final varnish. Or if you wish, you can stop with the very thin coat of varnish, using it as a varnish coat. Many artists use retouch varnish in this way or they'd never be able to enter their paintings in competitions, exhibits or even sell them. One artist who is a frequent contributor uses this method and if the painting is sold, he has the buyer return the painting at the end of the year and he gives it the final varnish.
    Meanwhile, the thinned down varnish has protected his painting and kept it clean for the final varnish coat."

    Summer
    PaulBedavison
  • dencaldencal -
    edited December 2017
    ;) PaulB

    The polymers in oil paint will be surface touch dry in two weeks depending on temp and humidity (T&H)
    Hard shell curing will be evident in three to six months, again T&H.
    Hardening and shrinking will progress over the next two to five years T&H.

    Using SDM and varnish will slow polymer curing.

    It is possible to use a Shore standardised polymer hardness test or some form of Heath Robinson equivalent.

    More can be achieved at the front end of the process to speed drying.

     ;)  use faster drying paint.
     ;) use thinner, leaner mixes
     ;)  use a siccative, metallic dryer or Liquin
    ;) Create  warm dry environment
     ;) paint in thin brushstrokes and avoid impasto
     ;)  build a drying box with insulation and a lightbulb, fan and thermometer
     ;) use Griffin Alkyd Oils
     ;) build an oxygen tent to accelerate curing
     ;) use Graham Alkyd walnut oil.



    Denis


    PaulB
  • Can also be used as a flamethrower. These and 8-year-olds help keep the fire departments in business.
    [Deleted User]
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