Panache - 18-10-2010 at 03:36
i use a domestic dishwasher because i haven't as yet come across an affordable lab one. I usually use it with a couple of the dishwashing blocks plus
any waste caustic i have accumulated plus any alcohols i have vapped off from the rotovap. This tends to work the best. However it is the worst
dishwasher ever made i believe, it has a 1/6 star rating, i think they got a work experience kid to design it. I recently got another better one for
free so i'm going to rip out the upper drawer on the current one and use it for larger items.
Anyone got any useful tips?
Rogeryermaw - 18-10-2010 at 08:37
how does it get the inside of flasks? still , that's a pretty good idea. can you run it dry to preheat glassware for moisture free reactions?
peach - 18-10-2010 at 12:42
I quite often slip things into the kitchen dishwasher.
Things I know aren't in anyway toxic.
Usually, it can't do a good enough job on the really bad stuff, but will do an okay job on something that's reasonably clean or that'll go aqueous.
I'd try to work out what the plastics are in the chambers and pump. If you undo the sides on it, you'll probably find molded chambers and paths for
the water to flow around - along with insulation. I would be willing to bet, those will be reasonably okay with quite high concentrations of sulphuric
and base - that they're propylene or MDPE / HDPE. I'd check the pump diaphragm as the main suspect; since it is continually flexing, which will
massively increase the chances of it failing. Try opening it and wiping a bit of strong acid or base over it, and watch for it it coming off on the
cloth or cracking. It's probably neoprene or rubber, and will be okay with it.
You can also reverse engineer it and still save money on a lab washer. E.g. rip out all that junk in the way and bypass it with something more
resistant. Possibly, including the diaphragm.
Something I've been wondering more about is biological washing powder. Enzymes can eat through organics better than some very serious acids or bases,
with no where near the risk.
Running litres of solvent through one is obviously a very bad idea; I would certainly not recommend any solvents in there (the plastics & rubbers
will rot / distort or it'll explode and engulf the kitchen in a fireball). But acid / base washes you may get away with. I'd start with the biological
for organics.
I would be careful using things straight out of it as well. Surfactants are very powerful and can entirely ruin phase boundaries in tiny quantities.
Equally, the last cycle of a kitchen based dishwasher usually involves a salt.
It doesn't really matter if it looks a bit worn out, but the insides are universally stainless (probably some low grade) which won't react too
severely with acid / base washing.
Provided you strategically position ports, it will get inside them. I put test tubes in the cutlery rack, so the openings are pointing at the jets.
Dishwashers are funny things. Like microwaves. Supposedly time saving 80's gadgets, yet often not effective.
And, if you're still eating microwave dinners, damn........... 
give up on life now, you have become the colour grey.
[Edited on 18-10-2010 by peach]
aonomus - 18-10-2010 at 13:52
The biggest difference between a commercial lab dishwasher and a home one is the ability to switch between tap water and DI water. Temperature ramps
and special detergents aside, if you just loaded a dishwasher with alconox and ran a cycle with a tap water rinse, you would still need to do a DI
rinse. A commercial glassware washing machine will drain the detergent cycle, do a tap water rinse, then a DI rinse (or however many is programmed
into the PLC).
All the other features are mainly gravy, heat settings, extra detergent cycles, special racks for odd glassware, etc. Stainless steel for detergent
resistance (note that commercial detergents are not just surfactants, but things like CIP-100/CIP-200 that are pH 0/11 and can cause corrosion to alot
of surfaces that aren't designed with that in mind).
Now, if you can program a microcontroller to do the job of a PLC, and add in a few solenoid valves to put in a DI wash, you essentially have a
commercial glass dishwasher.
peach - 18-10-2010 at 21:37
I found washing machines have a ton of free solenoids in them. You have to use them in the normally closed mode though, to inject water over a few
minutes and then switch off, or they'll overheat.
It would be nice if they did the DI as well, but you could always give them a rinse by hand. That stage should be fairly easy compared to the
scrubbing and washing.
If there's a rinse setting on there, you're one step ahead. You may not even need to use a solenoid. You could run a normal program, wait for it to
finish and then turn a manual plumbing valve to switch it over to DI, then hit rinse.
I was having a look at the Alconox page. Like with the NaOH and aluminium shavings in it, I am somewhat skeptical about how special that stuff is, and
would be willing to bet a number of the products are normal active ingredients minus the dyes, perfumes and foaming agents. If you have a search
around, the guys selling stuff to make soap and toiletries at home often sell the raw active ingredients, so you can avoid things you don't want in
there.
We have a brand of cleaner called ClitBang... erm... CillitBang in the UK, that is renowned for shifting pretty much everything. Then there's big
boxes of washing powder.
I suspect foam will be your main problem using them. It can sometimes leak out round the door seal if I put dish washing soap in there. More of a
problem, the jets won't be squirting very hard due to the quantity of air in the media.
I'm skeptical having worked in a place producing commercial soapy based products and watched multiple brands covering various price spectrums from
budget poor person grade to high end yuppie grade all come out of the same machine, with almost identical things on them (bar the perfume) and the
only difference being the picture on the pack it went into. Some of these would be worth tens of pence, others, people would pay £3 a pack in their
constant quest to rid themselves of germs.
The same is true of toothpaste. Most of it comes out of GlaxoSmith K factory somewhere near London and it's the same base in all of it, some of it
just has a stripe in it.
I'm also pondering about loading the washing machine with drinks bottles, as it'll do 1600rpm. There may be a spin drier on the way that'll do 3000 as
well. Not all that precise, but perhaps useful for more basic things - e.g. emulsions and fine filtrations.
I have been looking into tars and dissolving them, and discovered the Polysorbate series (Tweens) are usually quite effective. You can certainly buy
those as raw materials from the soap guys.
Failing all this, fill it with nitric and then "blow the bleedin' doors off!"