White Pots
Arnold Trachtenberg via pbs (Mon, 22 Aug 2022 10:20:21 PDT)

Shmuel
I guess the elders in terms of sun protection were spot on 
Arnold

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On Monday, August 22, 2022, 12:41 PM, Shmuel Silinsky via pbs <pbs@lists.pacificbulbsociety.net> wrote:

One can help make lighter-colored plastics more UV-stable by adding ZnO as
the white pigment...

Aha! So those stereotype old ladies on Miami beach with zinc oxide ointment
triangles on their noses really had something there! Never underestimate
the wisdom of the elders.

Shmuel
Jerusalem Israel
Zone 9b

On Mon, Aug 22, 2022, 2:08 AM Microsoft.com Team via pbs <
pbs@lists.pacificbulbsociety.net> wrote:

I am Alberto Castillo, in Buenos Aires. I have been using white plastic
containers for the bulb collection for some 15 years. They are used 5
gallon/20 litre buckets, well known  for selling paint, plaster, etc., and
they were tried at first due to the difficulty of finding really big pots.
Results have been excellent, the main problem being that their useful life
is variable, some becoming dangerously brittle after a couple of years,
others lasting ten years with no visible change. This speaking of white
plastic buckets. What has been just mentioned by Bob in a previous message
on container color and durability is a hundred percent exact in my
experience, grey and black buckets seeming eternal. Many of the (white)
buckets are in full sun and they are very useful to maintain mixes cooler
enough to avoid damage to the plants during our very long very hot summer.

Enviado desde Correo<https://go.microsoft.com/fwlink/?LinkId=550986> para
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De: Robert Lauf via pbs<mailto:pbs@lists.pacificbulbsociety.net>
Enviado: domingo, 21 de agosto de 2022 19:28
Para: Rick Rodich via pbs<mailto:pbs@lists.pacificbulbsociety.net>
CC: Robert Lauf<mailto:boblauf@att.net>
Asunto: Re: [pbs] White Pots

It is because embrittlement isn't caused by heat; it's caused by
radiation-induced cross-linking of the polymer.  The carbon black keeps the
UV from penetrating deep into the polymer and doing the damage.  One can
help make lighter-colored plastics more UV-stable by adding ZnO as the
white pigment, which is often done in higher-value plastic components like
garden furniture, but too costly for the really cheapo things like
semi-disposable pots.  The more high-value things also typically have a lot
more plasticizers in the formulation, which is also largely prohibitive in
thin plastic pots.  As they say, you get what you pay for!
Same reason white plastic labels become brittle after two years (or less)
in the sun.  Too bad they don't just get wrinkly like we do after years in
the sun....
Bob  Zone 7, getting some welcome rain and finally cooler temps.  A few
Lachenalias are waking from their summer siesta.
On Sunday, August 21, 2022 at 06:11:26 PM EDT, Rick Rodich via pbs <
pbs@lists.pacificbulbsociety.net> wrote:

I find that white plastic pots seem to turn brittle much faster.  Kinda
counter-intuitive. Rick Rodich

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