mirrored acrylic 'pox/cancer'

[John Noell]

Some of the mirrored acrylic we have done is coming down with some kind of pox. At first, it only showed up after several weeks and only along the edge where the awards were wedged into wooden bases - no where near the engraving. Now it is cropping up in the middle, adjacent to engravings. The first set were painted on the back with black lacquer, this one was done with acrylic artist's paint (Liquitex medium body). Does anyone know why this is happening? (It also looks very similar to a common problem we have with commercial CDs here in the tropics.)

[Darren Null]

The main question would be: what causes commercial CDs to do that? Because it's quite probably the same thing happening.

Where I live is hot, but dry, so I don't get the full tropical experience and CDs don't bubble where I am (45-ish centigrade in summer), so it must be humidity and/or something in the air. Fungal?

Anyway, it started at the edges, so whatever it is -as seems perfectly reasonable- attacks at the boundary of acrylic and mirror layer. It was first apparent, you say, when it was wedged into wood bases. Wood is porous and can hold moisture, as well as a bunch of organic stuff.

The condition has progressed, seemingly. Acrylic artists paint is fairly inhospitable to organic life and is pretty well waterproof, so that shouldn't be it. (You can get bubbling by mixing incompatible paints, or by 2 layers of different car paints before the first one is properly cured (2 weeks sometimes)). In theory the bubbling has occurred by allowing humidity/compound X into the part that was lasered. The progression could be explained if you're using the same stock and the heat/sunlight/whatever has a chance to work on your materials; thus weakening it.

So. It's not heat, unless you're storing them somewhere silly (direct sunlight, under the stove etc). We're left with:
Humidity (AFAIK Fiji isn't THAT humid)
Salt air (I live 20 metres from the sea and my CDs are fine)
Improper storage (cool, dark, dry place is good)
Biological agent (fungus, acid...)
Something volcanic (sulphur?)
Other thing I haven't thought of.

Artists acrylic paint should cap the laser work off and stop bad things happening, so your effects are happening quite quickly. So the material has been weakened by something which causes the layers to want to separate (bad storage?) and the various layers are separating whenever you traumatise them; OR there's some agent -biological or otherwise- getting in there in the short time between lasering and putting paint in.

My money would be on the former theory. But everything above is just that: theory. I hope the above ramblings have helped some.

How long does it take stuff to get to Fiji from the mainland? Does it cost more to order it direct? What -in the air, climate, your house, anywhere-could be causing it?

EDIT: I'm in a hot place and I live close to the sea. Frankly. I can't tell you what is, but I can eliminate some stuff. Salt air, no. Heat, nah. The only layer separation I've ever seen on a CD is when I lasered one. OK, several.

EDITAGAIN: Your bubbling looks crystalline/fractal. It's either a clue or the way that particular photo looks.

[John Noell]

The fractal look is quite real. Every "lesion" has it. Humidity where I am is about 70% on average. :) (Whenever I go somewhere else I fell like I am drying into a prune.) It takes about 2 weeks to get stuff from Australia or New Zealand, our closest neighbors. This happended to some mirror used the next day after arriving from Australia and to some stored for 2-3 months. The unlasered panels are still perfect.

[Darren Null]

So it's when you traumatise the material. Expose the mirroring to the air.

Big time (salty) humidity could do that, I suppose. Particularly when you expose it to a chemical-rich surface to play with...although I would be immensely surprised in that case if the CDs and the acrylic mirror had the same patterns.
Compare the two.
And have a word with your local CD supplier, because I'm sure that they will have had this same conversation and may have better answers.

PS: I sit corrected. Fuji IS that humid.
PPS: I'm still just guessing...hope some of it is of some use. Let me know if you get a solution. And there's other, much clevererer chaps lurking on the creek who might be able to supply more than my feeble guesswork. Chemists, step forward!

[Frank Corker]

It is the humidity that causes it I think. I get this on romark products such as the gold if they are exposed to the elements (despite what they say about indoor/outdoor use). Once you cut it with the laser, the edges allow moisture to seep into it, same applies when you have engraved it, allows the water in. I can only suggest that you coat it with clear waterproof varnish and do some tests to see how it copes with it.

[Darren Null]

Another thought has slowly formed in my head...what are you using to clean the excess colourfill off with? Possibly using a less powerful cleaning agent or letting the paint dry fully before cleaning the excess off may help.

I know that using spirit-based marker pen on CDs and DVDs causes the surfaces to separate over time (about 18 months). Maybe you're getting the same effect here.

Something to try, anyway, as there's not a lot you can do about the humidity.

[John Noell]

The first set was gently sprayed and not touched except for insertion into the wooden bases. In the 2nd set I was applying the artist's acrylic with a brush so no excess was removed in either case. These were handled quite gently (to avoid scratches). It is only the master-stamp type CDs that go bad (usually starting at the edges), not recordable ones. (And we see fewer and fewer master types as Fiji has incredible media piracy. No one rents DVDs here, they sell you a copy to keep, for F$1 (about $0.53 USA.)

[Roger McDowell]

I agree with many of the other responses that this problem is most likely associated with moisture attack at exposed surfaces, edges and such. But I have also had some mirrired acrylic that just seemed to have poor adhesion of the mirror to the acrylic. Take a small piece of duct tape and see if will pull the mirrored layer off of the back of the acrylic. Don't know of any solution to this problem but I have returned some acrylic that was affected by this problem.

Good Luck