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Tue Dec 10, 2024 12:29 pm

What I wrote to the sunglass company...

I want to alert you to a problem with sun glasses you manufacture. I had bought two pairs of your Completion sun glasses, SRO 119 at Rite Aid. The first pair seemed fine upon purchase, I wore it the day of purchase while Kayaking over a couple hours. I also applied sun screen to my face, hands, and arms. I was careful not to damage the glasses, never dropped them, nor set anything on them. When I got home I set the glasses on my kitchen counter, the next morning the frames near the nose bridge had cracked. I returned the broken glasses to Rite Aid for a replacement. When I selected the replacement, I was very careful to examine them for any defects, cracks and such, they looked fine. I then used the replacement that day, again wearing sun screen. Again, the next day, same thing, the frame came apart, cracked in several spots. The glasses just fell apart while sitting on my table. (image 1.) What's happening here?

I then got to thinking that maybe the problem is related to the sun screen. Plastics can be suseptable to Enviromental Stress Cracking, (ESC). Certain chemicals can cause the enviromental conditions that cause ESC, which happens when a plastic part is under stress, even molded in stress, and is exposed to the chemical. Under ESC conditions, the bonds between the plastic molecules can be broken, resulting in part failure.

I took the second pair of broken glasses and did an experiment overnight. I placed a dab of sun screen on the side ear piece and put a small amount of stress on it using a weight. I also put the same stress on the new unused pair of glasses, with no sun screen as a control sample. (see image 2.) The next morning, the sun screen exposed side frame part was cracked under the sun screen, (see image 5.). The control sample with no sunscreen was not cracked, even though it was exposed to the same bending stress. This is pretty conclusive, the failures are do to ESC from the sunscreen!

I then noticed that on the control sample glasses I accidently got a finger print of sun screen on the frame near the left side of the nose bridge while setting up the test, and it had cracked, despite it not be stressed by the wieghts. I then did a second experiment by placing a dab of sunscreen on the unused control sample glasses on the unbroken right side of the nose bridge, and left it over night on my kitchen counter, completely unstressed. (see image 3). The next morning it too had failed. (see image 4). Evidently there is residual stress in the frame from the moulding process, allowing ESC to occur with exposure to sun screen.

The sun screen used is made by Day Logic, a Rite Aid house brand and contains commonly used sun screen chemicals, including...

Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone (see image 6 for the label)

Among chemicals know to cause ESC in plastics are Esters, Ketones, Aldehydes, Aromatic Hydrocarbons, and Chlorinated Hydrocarbons. (see the attached pdf file below, Environmental Stress Cracking, The Plastic Killer, by Jeffery A. Jansen, Advanced Materials and Processes, June 2004)

Of course it is reasonable to conclude that sun screen will he used with sun glasses. Thus the glasses are really not fit to be merchantable, as failure occured in as little as 12 hours, even from incidental exposure to a finger print of sun screen.

I have included a Wikipedia link to ESC for your reference, a very brief description of molded in stress issues, and the short paper by Jansen on ESC that includes a list of chemicals I referenced that can cause ESC failures.

Tue Dec 10, 2024 12:43 pm

zerotofifty wrote: The sun screen used is made by Day Logic, a Rite Aid house brand and contains commonly used sun screen chemicals, including...

Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

Those are the most common sunscreen actives/filters, and I developed procedures to assay for them in such mixture in sunscreens in one assay. Because sunscreen actives absorb in the upper UV range and are present in high levels compared to most other drug actives, the sample matrix most always has no effect on the assay so the main concern is to separate all the actives from each other and assay in one test procedure.

Tue Dec 10, 2024 1:22 pm

Cusser wrote: zerotofifty wrote: The sun screen used is made by Day Logic, a Rite Aid house brand and contains commonly used sun screen chemicals, including...

Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

Those are the most common sunscreen actives/filters, and I developed procedures to assay for them in such mixture in sunscreens in one assay. Because sunscreen actives absorb in the upper UV range and are present in high levels compared to most other drug actives, the sample matrix most always has no effect on the assay so the main concern is to separate all the actives from each other and assay in one test procedure.

My father created what is now known as the first sunscreen SPF 15. I don’t think they had SPF ratings at the time. It was intended for Albinism and Government related stuff :wink: He was in charge of making this Top Secret powder in to a topical lotion. Nobody could do it at the time. He said this top secret powder was really strange how it reacted to other chemicals. For a goof he mixed it with Vaseline and it turned into what seemed like the consistency of old chewing gum. This powder baffled him until one day an associate told him what the powder was and dad created the recipe. He told me the ingredients did some funky stuff to various materials. I believe this to be late 50s early 60s. I imagine the formulation and ingredients are different today but still might to some funky stuff.

Tue Dec 10, 2024 1:46 pm

Xevin wrote: Cusser wrote: zerotofifty wrote: The sun screen used is made by Day Logic, a Rite Aid house brand and contains commonly used sun screen chemicals, including...

Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

Those are the most common sunscreen actives/filters, and I developed procedures to assay for them in such mixture in sunscreens in one assay. Because sunscreen actives absorb in the upper UV range and are present in high levels compared to most other drug actives, the sample matrix most always has no effect on the assay so the main concern is to separate all the actives from each other and assay in one test procedure.

My father created what is now known as the first sunscreen SPF 15. I don’t think they had SPF ratings at the time. It was intended for Albinism and Government related stuff :wink: He was in charge of making this Top Secret powder in to a topical lotion. Nobody could do it at the time. He said this top secret powder was really strange how it reacted to other chemicals. For a goof he mixed it with Vaseline and it turned into what seemed like the consistency of old chewing gum. This powder baffled him until one day an associate told him what the powder was and dad created the recipe. He told me the ingredients did some funky stuff to various materials. I believe this to be late 50s early 60s. I imagine the formulation and ingredients are different today but still might to some funky stuff.

Top Secret Powder, eh...?

Tue Dec 10, 2024 2:14 pm

Xevin wrote: My father created what is now known as the first sunscreen SPF 15. I don’t think they had SPF ratings at the time. It was intended for Albinism and Government related stuff :wink: He was in charge of making this Top Secret powder in to a topical lotion. Nobody could do it at the time. He said this top secret powder was really strange how it reacted to other chemicals. For a goof he mixed it with Vaseline and it turned into what seemed like the consistency of old chewing gum. This powder baffled him until one day an associate told him what the powder was and dad created the recipe. He told me the ingredients did some funky stuff to various materials. I believe this to be late 50s early 60s. I imagine the formulation and ingredients are different today but still might to some funky stuff.

Para-aminobenzoic acid (PABA) based maybe? That fell out of favor by the 1980s, and has been banned since 2021. Worked really well, though!

Tue Dec 10, 2024 4:10 pm

Tue Dec 10, 2024 6:05 pm

Xevin wrote: Cusser wrote: zerotofifty wrote: The sun screen used is made by Day Logic, a Rite Aid house brand and contains commonly used sun screen chemicals, including...

Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

Those are the most common sunscreen actives/filters, and I developed procedures to assay for them in such mixture in sunscreens in one assay. Because sunscreen actives absorb in the upper UV range and are present in high levels compared to most other drug actives, the sample matrix most always has no effect on the assay so the main concern is to separate all the actives from each other and assay in one test procedure.

My father created what is now known as the first sunscreen SPF 15. I don’t think they had SPF ratings at the time. It was intended for Albinism and Government related stuff :wink: He was in charge of making this Top Secret powder in to a topical lotion. Nobody could do it at the time. He said this top secret powder was really strange how it reacted to other chemicals. For a goof he mixed it with Vaseline and it turned into what seemed like the consistency of old chewing gum. This powder baffled him until one day an associate told him what the powder was and dad created the recipe. He told me the ingredients did some funky stuff to various materials. I believe this to be late 50s early 60s. I imagine the formulation and ingredients are different today but still might to some funky stuff.

Oh yeah!....lots of powders with magic powers like that!. I work in what is effectively the industrial printing industry (printed electronics, medical devices and Industrial products).

We have spray coatings, dip coatings, powder coatings...and the printing inks for each print platform (say screen print vs flexo vs offset vs pad print vs inkjet)....all have wildly different pigment systems, solvents, resins, binders and curing systems.......and most especially....they have wildly different "modifiers" and "fillers".

Peoplethink "fillers" are describing some kind of cheap junk to take the place of expensive stuff. Nothing can be further from the truth.

One of the biggest fillers used to modify rheology of fluids ...are "Talc's"

Instantly people think ofg talcum powder. Nope.

There are talcs than can turn a liquid to solid (depending on the liquids polarity)...or turn a liquid even more liquid....or cause a liquid to no longer shear thin but instead to shear thicken (its called dilatency).

There are over 100 types of talc, each with a very specific set of characteristics. Some are nearly nano-particle size others are larger.

An endless varoety of what can be accomplished with these "powders". Ray

Sat Dec 14, 2024 7:02 pm

TDCTDI wrote: outcaststudios wrote: oil is a thinner for most paints so...

Yes, except that vegetable oil doesn’t/shouldnt thin enamel paint.

its never a good idea to pretend you know more about paint than an artist. artists spend their whole lives making paint, hoarding oxides and grinding and hand lapping paints. they try different formulas and they talk about paint a lot. go ahead id like you to explain why you made the statement you made.

Tue Sep 09, 2025 6:44 am

hobthebob wrote: Yeah the Filet O' Fish is pretty good. All things considered, that's pretty cheap food, but again, the burger was probably trash...

Near me in Austin restaurants all around are increasing prices slowly, and even Sonic discontinued their happy hour discounts on food. I'm starting to see that I should just go home for or pack lunch now.

Especially since not only are wages increased, but almost EVERY SINGLE restaurant asks if you wanna tip them. I had a bartender give me a nasty look when I picked up a pizza and didn't tip her. I'm sorry, I didn't realize running into the back for 30 seconds is worth a $2 tip! I'm going to stop tipping, just realizing how much wages are increasing.

I ant tipping for fast food, hell their minimum, yes minimum wage is 20 bucks an hour out in my parts. 40K a year for handing me fast food. Of course I rarely eat at them places.