Why are liquid developers packaged in HDPE?

Since photographic developers are so sensitive to oxidation, why do manufacturers almost always package them in ordinary HDPE bottles? Why not PETE bottles instead?

Finally, how important is it to keep developers away from light? I'm assuming it must not be that important if most developers are not packaged by the manufacturers in dark bottles. I'm wondering if the recommendation to use brown bottles is nothing more than a myth. I rather like using clear PETE because you can easily see discoloration.

Does anyone have answers for these two questions over which I have been agonizing for years? Ok, well not actually agonizing, but certainly curious about.

-Dave

Packaging regulations as some chemistry is hazardous. If you look at household bleaches etc they aren't in PET either nor are any otherhazardous liquids.

PET bottles aren't safe and I've had them break down in about 18 months maybe 2 years, in an accident they are far more likely to split/break.

Ian

Thanks, Ian.

I suspected it might have something to do with shock resistance. I use gallon size PETE bottles for Dektol and the sides are sucked in as the developer absorbs the oxygen from the air inside. DOing that repeatedly is going to eventually result in cracking.

But what about the dark versus non-dark containers? Myth or reality?

I assume PET bottles non-corroded by their content as unbreakable under practical lab situations.

There are even PET-based bottles with enhanced oxigen barrier. (In general there is a variety of PET resins for bottle-making.

Furthermore there are co-polymer bottles on the market that yield greater oxygen barrier with PE-bottles.

PET seems to be more brittle than HDPE, so it might be more prone to break if you drop it. I use them in one gallon size which makes them pretty heavy when full.

I also have some HDPE bottles that have a nylon interior coating that is supposed to improve the barrier qualities, but I'm not sure exactly how that plays with photo chemicals. Nylon's permeability can decrease in water, or so I've read. On the other hand I have some Xtol stored in them that was mixed up in July of 2011 and it worked fine as of last weekend.

I have a lot of usage of 2L PET single-use bottles filled with water whilst hiking. They often fell about a 1.5m in various states of filling and never broke. There were kinks in the worst case.

I just ordered and received (haven't used yet) a quart of Legacypro eco-pro paper developer, which has been reported to be ascorbic based and therefore sensitive to oxidation. It is packaged in a brown PETE bottle and, as delivered, is slightly squeezed in at the side. Apparently, when there's a unique need for an oxygen barrier, PETE is used.

Sal Santamaura said:

Apparently, when there's a unique need for an oxygen barrier, PETE is used.

Click to expand...

That also goes for HDPE, in the case of the Legacy Pro product it's more likely cost in their choice. Ilford and Agfa (and successors) sell their liquid ascorbic based devlopers in HDPE

Ian

Sal Santamaura said:

...Apparently, when there's a unique need for an oxygen barrier, PETE is used.

Click to expand...

Ian Grant said:

That also goes for HDPE, in the case of the Legacy Pro product it's more likely cost in their choice. Ilford and Agfa (and successors) sell their liquid ascorbic based devlopers in HDPE...

Click to expand...

According to this

PET passes less than 1/8 the oxygen that HDPE does. I'm not sure what relative costs are, but, given that HDPE is ubiquitous and PET isn't, suspect the latter is more expensive, not less.

There are also composite bottles which contain more than one layer of different plastics. Such bottles have better oxygeb blocking than single layer ones. Such composites are included under a SPI code of 7 (the number in the recycle triangle). You often see them used for nutritional drinks where oxygen can cause flavor changes.

Sal Santamaura said:

...given that HDPE is ubiquitous and PET isn't, suspect the latter is more expensive...

Click to expand...

Some quick searching confirms that suspicion. Not photo chemical containers, but still an apples-to-apples comparison showing PET roughly 50% more expensive than HDPE:

Those price differentials may well be down to production volumes affecting prices.

PET bottles are in wide scale use for low value products, Coke bottles, mineral water etc, the equivalent HDPE bottle needed to prevent loss of pressure, gas permeability is very much thicker.

However the thicker HDPE bottles are very significantly safer to the extent that quite corrosive chemicals like concentrated acids, Nitric, Sulphuric, Hydrochloric, Fluoric and also alkalis are supplied in HDPE bottles. In fgact it's now preferred to glass.

Nothing hazarous can be sold in PET of the thickness we see in common use and it's brittle unlike HDPE.

Ian

Only at APUG could we have a coherent and useful thread about the merits of different plastics for storing chemistry.

The expertise here is terrific.

Yes, very interesting discussion. I use random plastic bottles from the recycling bin for most of my chemicals, I'll have to check and see what types of plastic they are.

Thanks for all the discussion. I have to admit that the PETE bottles I use don't seem as thick as the HDPE bottles, so maybe the difference in performance isn't quite as great as the raw numbers would indicate. My wife gets bottled water in PETE bottles that are so thin it's like holding a water balloon.

Just as an aside, I also looked up Saran wrap since that has been mentioned as a way to improve the cap seal on bottles for storing photo chemicals. It turns out that Saran is an exceptional oxygen barrier which is why it keeps food so fresh. Other plastic wraps use less effective polymers. Unfortunately, Saran wrap is no longer made from Saran (polyvinylidene chloride) for environmental reasons. Now they make it from ordinary LDPE.

After reading this and a few other discussions, it's safe to say that my Datatainer bottles aren't any good for long term (6-8 month) storage? I'm still a relative newbie to this. I'm still in the oooh and ahhh stage, and trying to perfect my technique.

Hi All,

I know somebody is going to be offended (and it is not my intention), but this all seems like we're looking for a problem where none exists. I've had T-Max developer last for years in it's container (opened and used slowly) and Xtol last for close to a year (I used it up) in those goofy old accordion bottles. I've never had Dektol go bad before it was used up. I know I've written this multiple times, but if your chemistry is going bad, you're not making enough photos! ;>)

Neal Wydra

Speaking as someone who has spec'ed out packaging, I think understand. When specing out packaging usually there are two things you usually consider.....oxygen permiability or water vapor. For developer, the gas/oxygen permeability is what you care about and oriented PET (like blow molded bottles) has about 1/50th of the O2 permeability of HDPE. The previous post that mentions a lower barrier number is probably PETG(ref. here HDPE is a lot cheaper to blow mold and has very good moisture barrier properties. The reason that the PET developer bottles suck in is that the oxygen gas in the bottle is going into the solution and oxidizing the developer. The bottle doesn't allow air into the bottle to replace the oxygen being consumed by the oxidizing developer so it sucks in. The HDPE wouldn't suck in because the air can more easily get through the bottle to replace the oxygen........bottom line is that PET is a good bet. Personally, I use glass because it is even better.

Dave Krueger said:

...I have to admit that the PETE bottles I use don't seem as thick as the HDPE bottles, so maybe the difference in performance isn't quite as great as the raw numbers would indicate. My wife gets bottled water in PETE bottles that are so thin it's like holding a water balloon...

Click to expand...

The eco-pro developer PETE bottle is far thicker than those water bottles. Off topic, my wife also buys bottled water. What do they think is wrong with the tap water for drinking?

Dave Krueger said:

...Saran wrap since...has been mentioned as a way to improve the cap seal on bottles for storing photo chemicals. It turns out that Saran is an exceptional oxygen barrier which is why it keeps food so fresh. Other plastic wraps use less effective polymers. Unfortunately, Saran wrap is no longer made from Saran (polyvinylidene chloride) for environmental reasons. Now they make it from ordinary LDPE.

Click to expand...

Which is why I store mixed XTOL in glass bottles with teflon-lined caps. I also decant liquid concentrate developers into those bottles after using enough that their original containers can no longer be squeezed free of air before closing and/or their original caps won't seal tight enough to keep those containers squeezed.

So can we conclude then that if you have the choice, reusing a PET bottle to store mixed developer in is a better option than reusing a HPDE bottle? For stop and fix, I don't think it matters. And if the PET bottle gets brittle after a few years, you just replace it with another PET bottle that was otherwise going into the recycling. My Se toner bottle is at that point and I just finished a bottle of Tonic. Lucky me.

Here is some information on plastics used for bottles. Of particular interest is the permeability values.

HDPE Semi-rigid, translucent, very tough, very good chemical resistant
to dilute acids, dilute alkalis and alcohols, moderate resistance to
oils and greases, low water absorption, easily processed by most methods,
low cost.
LDPE Flexible, translucent/waxy, weatherproof, good low temperature
toughness (to -60? C), easy to process by most methods, low cost, very
good chemical resistance to dilute acids, dilute alkalis and alcohols,
moderate resistance to oils and greases.
PC Rigid, transparent, outstanding impact resistance (to -150? C) good
weather resistance, dimensional stability, resistant to flame, good
resistance to dilute acids and alcohols, very good resistance to oils
and greases
PC Rigid, transparent, outstanding impact resistance (to -150? C) good
weather resistance, dimensional stability, resistant to flame, good
resistance to dilute acids and alcohols, very good resistance to oils
and greases
PET Rigid, clear, extremely tough, good creep and fatigue resistance,
wide range temperature resistance (-40 to 200? C), does not flow on
heating, very good resistance to dilute acids, dilute alkalis, alcohols,
oils and greases
PVC Rigid or flexible, clear, durable, weatherproof, flame resistant,
good impact strength, good electrical insulation properties, limited
low temperature performance, very good resistance to dilute acids,
dilute alkalis, good resistance to alcohols, oils and greases


.........................................................O2 CO2
---------------------------------------------------------
|EVOH |Ethylene vinyl alcohol copolymer | 2 | - |
|HDPE |High density polyethylene | 2900 | 9100 |
|LDPE |Low density polyethylene | 7900 | 42500 |
|PC |Polycarbonate | 4700 | 17000 |
|PET |Polyethylene terphthalate | 95 | 240 |
|PVC |Polyvinyl chloride | 120 | 500 |
---------------------------------------------------------
values are for 1 mil thickness, units cm3/m2.24h.atm

OK, but what do they mean in practical sense? If HDPE has a value of 2900 for O2, it passes 2900 cm^2/m^2.... Does that mean death to developers or is that an acceptable value? I have been storing mine in HDPE bottles and it is fine for all practical sense for over 6 months period. (so for my purpose, it's perfectly fine....)

For comparison purpose, do you have such data for Polypropylene which I did notice some color change.

Just to clarify -- most of the bottles I see that start with PET end with an "E" -- so they are PETE bottles. May I assume that the general characteristics attributed to PET apply to the subset of PETE bottles?

PET and PETE mean the same.

Glass is the best. Started with glass, used plastic, now back to glass.