AR glass vs AR acrylic

[Rainbow]

For a picture that has to be unavoidably hung in direct sunlight, I know there is no ideal solution but would you recommend AR glass or AR acrylic as the best option under the circumstances. Thanks.

[Not your average framer]

I'm not sure that this makes any sense at all. Tha potential amount of UV light in direct sunlight is literally enormous and even the very highest ratings available of UV blocking are very unlikely to provide a viable level os UV blocking which is suficient to gine the artwork any meaningful life span, before it's financial value is rendered valueless due to fading. I'm not joking, it is very likely that just a single summer, will be enough to rein the artwork. Sorry, but this is a crazy idea!

[Rainbow]

I appreciate that, Mark, but like I said - it's unavoidable. I'll advise the customer anyway to close the blinds when the sun is shining, but even when the sun isn't shining, it will still be in direct light. The picture doesn't have any significant financial value.

[Not your average framer]

Fair enough!

[JFeig]

The only way to solve the problem is to have a quantity of "back-up" images that can be swapped out when the fading is discovered to be a problem.

[Rainbow]

That's a good point, I'll suggest that to them, thanks.

[Justintime]

IMO temperature and humidity changes would be a major consideration with direct sunlight. Doesn't acrylic conduct heat a lot less than glass?

[Not your average framer]

Well yes. So which is more preferable and why? Are we talking about heat tending to cockle the artwork more easily, or maybe that heat will increase micro condesation inside the frame? Just interested to know where you are coming from. It's not something which I have actually thought about until now.

[Justintime]

I think you've answered your own questions.

[Not your average framer]

Thanks Justin,

I just wondered if you had thought of anything which I might have missed.

[Justintime]

Only other thing that comes to mind is that if you go for acrylic, make sure to leave extra expansion room in the rebate. Depending on the size and thickness, acrylic can need considerably more than 1mm each side. I don't have the figures to hand, but I believe Rob Markoff posted a link to lab tests on this in the framing.academy facebook group. I vaguely remember mention of a 4mm expansion gap for large pieces..

[Justintime]

In which case I imagine Volara tape in the rebate would be useful.

[Not your average framer]

I would expect that the degree of expansion with temperature changes would mainly apply on larger pieces of acryilc, so on smaller pices perhaps you would not need to add any extra clearance compared with glass. Considering the fact that most mouldings only have a rebate width of 6mm and acrylic being more flexible that glass perhaps needs a bit more support around the edges because of this, perhaps adding a flat slip inside the rebate between the glass and the rebate edge might be something to consider as a possible option.

I often add flat slips in side larger sized frames, just to increase the apparent moulding width as it ofter just looks more in proportion. I also like deeper mouldings for larger sized frames as it gives me space to add a sub-frame to add extra support to the often narrow frames which so many customers seem to like on large frames.

[Steve N]

In my old workshop the upstairs had a slopping ceiling with 2 Velux windows on one side, on one sunny afternoon I had stored a small USA flag framed in Conservation 99% glass, it was only up there for 2 hours, the customer came to collect, I went upstairs to fetch it, when I got up there y, the sun was shining on the framed flag, and there was condensation on the inside of the glass, lucky the glass was spaced off the flag. I took the frame back downstairs and showed the customer it, while we were talking about it and how it happened, the condensation dissipated, the customer was happy to take it away, and kept an eye on it, when he came in again to get something else framed, he said it had never happened again.

I made some frames up with white sheets on and put these in the windows to still allow the light through, never had the problem again, but I always placed and finished frames way out of the way from the sun

[Rainbow]

Good points, thank you all

[grahamdown]

Are we talking AR or UV protection?

In my experience when it comes to AR acrylic its usually done with a fine etching on one surface rather than the coatings you get with glass - or am I wrong?

[Rainbow]

Hi Graham, the customer has asked for anti-reflective, but I'll recommend the highest possible level of UV as well.