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MITRA Forum Question Details

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  • Polyester CanvasApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2019-03-24 17:53:34 ... Most recent comment 2019-03-25 16:40:35
    Flexible Supports Oil Paint Art Conservation Topics

    ​Apart from possible aesthetic considerations, a polyester canvas would seem a more ideal flexible support than linen or cotton, at least in longevity.  Less reactive to humidity, embrittlement and bacterial attack, it would appear almost perfect.  

    Except, what about heat?  What damage would occur should some future person try to iron it down to another support?   Would the polyester reach a temperature likely to cause damage in a way that say, linen wouldn't be in a similar procedure?  When using a polyester canvas should we make sure that we find some form of pre heat shrunk material?  Is this even available, or is it something already standard in polyester artist canvases?

Answers and Comments

  • EditDeleteModerator Answer

    We have had a couple of threads that are relevant to this topic. This one in particular

    and this as well

    As far as heat, a program trained painting conservator would test everything before any procedure. You could/should make their life easier by recording all of your materials and attaching that to your artwork (see our resources section). Finally, the heat used to line or consolidate a painting should fall below that of scorching a polyester fabric. The conservator would need to test, of course, but the temperatures indicated on a typical iron for ironing polyester fabrics is vastly higher than the temperatures used by ethical conservators.

    Finally, I do not believe that polyester fabrics can be pre-shrunk. One of their virtues is that they are not effected by moisture in the same way as natural fibers and do not shrink like linen and cotton.

    Brian Baade
    2019-03-24 19:40:37
  • ApproveRejectUn-ApproveUser Comment

    ​Thank you for your reply. Certainly much to consider.

    The pre-shrunk notion is regarding some form of heat shrink/setting.  Not wet and dry shrinking.  I just tested a strip of polyester 150ml long and by ironing it at "wool" setting one can get it to shrink it to149ml.  Further ironing at this highly precise temp (do I hear laughing?) doesn't seem to reduce it further.  (Increasing the temperature might risk visibly singeing it.)  Now perhaps one could just iron the polyester this way before stretching, but maybe that's not advisable.  Possibly any ironing is just a form of mild but unadvantageous damage.

    2019-03-24 22:06:16
  • EditDeleteModerator Answer

    At that point, I think that you are distorting and not really shrinking. I mean, you could ramp the heat up so high as to theoretically make a film out of it (hyperbole, I know). But that is way beyond what we need to deal with on this subject..

    Brian Baade
    2019-03-24 22:30:35
  • ApproveRejectUn-ApproveUser Comment

    ​I remembered something about polyester sailcloths being heat set in some manner.  And I stumbled across this from a site called 'Conservation Support Systems.'  Under lining fabrics, "polyester sailcloth"  "The sail cloth is removed from the production line before any finishes are applied; therefore it is free of all finishing resins, specially melamine-formaldehyde.  The fabric is scoured to remove all contaminants and then heat-set at 400F to tighten the weave.  This pre-shrinking of the material eliminates the possiblity of shrinking or warping during most lining process using heat setting techniques."

    Unfortunately it's only 5.5oz and perhaps too light to be used as a primary support.  I'd desire something closer to twice that.

    It's possible that this lining fabric might need to be more resistant to heat because it would be in more direct contact with the iron surface?

    BTW this 5.5oz is mentioned as "basis weight" and I come from a metric country.  Is there any deviation or oddity to this description?

    2019-03-25 15:38:38
  • EditDeleteModerator Answer

    Ah, so you mean industrially pre-shrunk as compared to studio technique. Got it.

    Again, most lining procedures would not call for temperatures above 150-180 F. Certainly nowhere near the heat you are talking about. Kristin and I often use a heavy weight acrylic fabric when we line which works wonderfully for our purposes. However, we do not add any additional sizing or ground layer and we coat it with a synthetic lining adhesive, so this may not be a good judge of its suitability as a painting substrate. 

    Brian Baade
    2019-03-25 16:40:35

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