Coffee filters, or Lab Grade Filters?

Mick Fagan · Apr 13, 2017

I recently read a suggestion to use lab grade rapid (coarse) filters, instead of coffee filters.

This was interesting to me, I have been using Melitta coffee filters for my photographic solutions, forever.

I did a quick online search for local to me product, it seems they are quite inexpensive and of an almost identical unit cost to my supermarket purchased Melitta coffee filters, which greatly surprised me.

I was wondering just what the differences are, and are they faster at letting solutions drain through?

For instance, I normally drain off either 150ml or 250ml of stock D76 solution through a filter sitting in a funnel. This can take some time, say 5 minutes, give or take.

The time thing is not important, the filtration aspect is my priority. That is, am I getting small enough filtration using a coffee filter, or will I get better filtration using lab grade filters? With the possible gain of filtration speed, as a by-product, to boot?

My current thoughts are, that if the cost is virtually identical, why not use something, that on paper, seems to be a better solution!

Mick.

mshchem · Apr 13, 2017

Hi Mick,
I worked as a bench chemist for 15 years. Filter paper is (was) expensive. There's all kinds of ways to filter. Probably the fastest is by using a sidearm flask, hooked up to a vacuum source and a Buchner funnel with a thick fiberglass mat filter. You could filter 5 liters in 2 minutes.
Fast lab filters are probably slower than coffee filters. The classic was fast, medium and slow. The slow was for quantitative analysis, you would collect the precipitate and believe me this takes for ever.

The fast qualitative papers are fast (relatively) a old standby was Whatman #2 paper, we were spending the companies money so we used 2V (pre-pleated) save you the time of folding. Whatman filters are expensive, a box of 100 18 cm circles not pleated are 35 USD. I get cheapo coffee basket type filters for a penny a piece and they are fast. But what the heck I love playing mad chemist, get your self a couple good funnels, learn how to pleat your paper, a ring stand will help to hold the funnel. I love folding filter paper, impress your friends.
Mike

bvy · Apr 14, 2017

I get a precipitate when I mix XTOL. A simple flat bottom coffee filter gets rid of it. I place it in a large funnel.

Anon Ymous · Apr 14, 2017

From what I've seen, cheap filters are the small diameter ones, which are not of much use IMHO. I've used two coffee filters together for better filtration and seem to do the job well.

EDIT: I only use two filters when I feel that there are very fine particles suspended. In any other case (nearly always), a single coffee filter is more than enough in my experience.

John Wiegerink · Apr 14, 2017

I started having problems with my replenished Xtol and also my homebrewed TF2 Alki fixer. I now filter both before development and before it goes back in the jug for Xtol and the same for the TF2 fixer. I tried a paper coffee filter in a funnel method, but soon realized that I might be dead before I could filter a liter. The filter would cling to the sides and do no filtering there with the only filtering taking place at the hole in the very bottom of the funnel. I then found one of those flat "gold" basket filters for a coffee pot and decided to try that. Now I use that, lined with a regular paper coffee basket filter, all set in my large funnel. Now it might not be "lab grade" filtering, but I don't really give a rats behind, 'cause it solved my problems very handedly. If it ain't broke, don't fix it!

Gerald C Koch · Apr 14, 2017

As I said before coffee filters are intended to filter out large particles like coffee grounds not fine precipitates as are encountered with photographic solutions. It has been my experience when making coffee that there is always some fine particles that get into the coffee. Now there are better grades of coffee filters but the cheap ones allow a lot to pass through. Student grade filter paper is not expensive and is far better than coffee filters. Avoid papers that have the word "analytical" in their name as they are expensive. That being said what is more important saving a few pennies or protecting your negatives from damage?

In addition how you use the filter paper makes a big difference in filtration speed. How the paper is folded is important. Coffee filters are just too flimsy to fold correctly for maximum filtration speed. There are several videos on the web showing how to correctly fold the paper.

https://video.search.yahoo.com/yhs/...=16d4ce52b0f5eb5b793453f60b30f74d&action=view

darkroommike · Apr 14, 2017

John Wiegerink said:
I started having problems with my replenished Xtol and also my homebrewed TF2 Alki fixer. I now filter both before development and before it goes back in the jug for Xtol and the same for the TF2 fixer. I tried a paper coffee filter in a funnel method, but soon realized that I might be dead before I could filter a liter. The filter would cling to the sides and do no filtering there with the only filtering taking place at the hole in the very bottom of the funnel. I then found one of those flat "gold" basket filters for a coffee pot and decided to try that. Now I use that, lined with a regular paper coffee basket filter, all set in my large funnel. Now it might not be "lab grade" filtering, but I don't really give a rats behind, 'cause it solved my problems very handedly. If it ain't broke, don't fix it!

For small filter + funnel the "matchstick" trick works to let a little space between filter and funnel. I bought a new coffee maker identical to my old one and use the new basket with ribbed sided to filter solutions, keeps the filter from sticking to the funnel. I use the old basket in my new coffee maker so there's not contamination (or chance I'll poison myself-LOL).

AgX · Apr 14, 2017

Gerald C Koch said:
Coffee filters are just too flimsy to fold correctly for maximum filtration speed.

All coffee filtes I ever came across here are already cut, folded and cemented into a laid flat cone.

Vaughn · Apr 14, 2017

Thanks for perspective, Mike (not you, darkroommike, the other mike from Iowa).

I have some H.Reeve Angel & Co. Genuine American Folded Filter Paper. The numbers 812 on the wedged shaped package. Slow as slow, but eventually filters my platinum developer. But I have also used cotton balls in a funnel for filtering Platinum developers -- I just want to get the chunks out.

carioca · Apr 14, 2017

I used to filter with coffee filters, but invested in lab grade filters for more consistency. My coffee filters were 'Melitta' brand and when I took a closer look at them with a loupe, I noticed that the perforation is different from center to edge. Towards the upper area, the perforation holes are much greater than at the bottom center area, probably because coffee has different size particles, the finer ones (obviously heavier) go to the bottom, the coarser ones being lighter rise to the top, so, different filtering in the same filter - to unpredictable for me. I now use different mesh lab grade filters to filter my solutions, depending on their density. For example, I also use replenished X-Tol and filter it with a very fine mesh filter (2-3 micrometers) with a Buchner funnel and vacuum pump (the same pump I also use for my vacuum easel, so no extra investment), it takes 1-2 minutes to filter 2 1/2 liters that way. Without the pump, it would take a few hours to drip through the same mesh filter. The results I'm getting were definitely worth the investment.

Martin Rickards · Apr 14, 2017

I remember 50 years ago, using a Whatman #42 for filtering barium sulphate. I wouldn't recommend it for filtering anything unless you've got a lot of time to kill. For general photographic use, I'd think coffee filters are good enough.

pdeeh · Apr 14, 2017

See if you can track down some Chemex FP-1 filter papers.
They are sold for coffeemakers but are 30cm diameter and appear to be a lab-type grade filter paper and are certainly robust enough for a fan-fold.
Though, I always forget that I got myself a box and end up using a Melitta.
Over here they are packed in boxes of 100 for about £8 which isn't super cheap but, as we all know, everything's cheap in America

Scott Micciche · Apr 14, 2017

I use the coffee filters that got the worst ratings for coffee flavor. These don't have any perforations. They are cheap, unbleached filters for Mr. Coffee pots. I use one of those single, pour-over contraptions, place the filter inside it and pour through to my required amount. 600 of them can be had on amazon for $20.

Gerald C Koch · Apr 14, 2017

Martin Rickards said:
I remember 50 years ago, using a Whatman #42 for filtering barium sulphate. I wouldn't recommend it for filtering anything unless you've got a lot of time to kill. For general photographic use, I'd think coffee filters are good enough.

To increase filtration speed when using lab grade filter paper:

1. Use coarse grade paper.
2. Fold the filter paper correctly. Watch the video.
3. Let gravity work for you. Allow the solution to stand and then decant the clear portion. Then you are only filtering a small portion of the liquid.
4. Invest in a filter funnel. This type of funnel has a long stem. The idea is to establish a column of liquid in the stem which creates a suction to pull liquid through the filter paper. Once again letting gravity do the work. Obviously this trick does not work for pleated paper.

Mick Fagan · Apr 14, 2017

What a great lot of replies, all of them with ideas to look at and/or try.

Gerald, as you are probably aware, it was one of your posts in another thread that got me thinking about filtration of my solutions.
Many thanks for the link to the video clip, doing that Origami folding trick is neat and looks easy as. I just practised on a piece of paper I cut into a circle, worked a treat. I'm now going to look for some relatively cheap lab grade filter paper.

To Mike and his previous use of a Büchner funnel, nice, but I don't think so for my set-up.

To all of the others, this has been an illuminating thread for what is generally a mundane darkroom practice. I thank you all.

Mick.

bvy · Apr 14, 2017

Gerald C Koch said:
That being said what is more important saving a few pennies or protecting your negatives from damage?

I don't get it. If a simple coffee filter works, why do I need lab grade? It's not about economizing for me. Before the coffee filter, there's precipitate. Afterwards, it's gone.

Kevin Caulfield · Apr 15, 2017

Interesting thread, Mick. Just curious about the need for filtration. Partly inspired by your own developer mixing, I've been mixing my own for a few years but haven't seen a need for filtration.

mshchem · Apr 15, 2017

John Wiegerink said:
I started having problems with my replenished Xtol and also my homebrewed TF2 Alki fixer. I now filter both before development and before it goes back in the jug for Xtol and the same for the TF2 fixer. I tried a paper coffee filter in a funnel method, but soon realized that I might be dead before I could filter a liter. The filter would cling to the sides and do no filtering there with the only filtering taking place at the hole in the very bottom of the funnel. I then found one of those flat "gold" basket filters for a coffee pot and decided to try that. Now I use that, lined with a regular paper coffee basket filter, all set in my large funnel. Now it might not be "lab grade" filtering, but I don't really give a rats behind, 'cause it solved my problems very handedly. If it ain't broke, don't fix it!

Excellent solution!

AgX · Apr 15, 2017

carioca said:
My coffee filters were 'Melitta' brand and when I took a closer look at them with a loupe, I noticed that the perforation is different from center to edge. Towards the upper area, the perforation holes are much greater than at the bottom center area, probably because coffee has different size particles, the finer ones (obviously heavier) go to the bottom, the coarser ones being lighter rise to the top, so, different filtering in the same filter - to unpredictable for me.

Interesting to know. But hard to believe to be intentional, seen the way paper is made industrially.

Doremus Scudder · Apr 15, 2017

Okay, I'm curious now, so I'll play devil's advocate.

What degree of filtration is needed for what? I manage to get negatives with absolutely no particulates on them without using any filtration at all. I use all solutions "one session" and dilute developer, stop and fix with tap water. Wash is in tap water. Final rinse is in distilled water (presumably filtered) with wetting agent.

When toning prints, as most of you know, I use replenished selenium toner. I filter it before and after toning with coffee filters or (horrors) a wad of paper toweling in a funnel. No particulates on the prints after toning and washing.

So, what is it you guys are using that gets particulates on your negatives? If the fixer is so old it is silvering out and/or sulfuring out, maybe the better solution would be to mix fresh?

And a related question: Assuming that we want to use some solution or other that has particulates in it that need filtered out (replenished developer or whatever). What degree of filtration is needed? Is "coarse" filter paper really a better filter than coffee filters? How fine a filtration is actually necessary?

Finally, what filter paper do you recommend? There's a bewildering assortment of them to choose from.

Best,

Doremus

Ian Grant · Apr 15, 2017

Like you Doremus I use coffee filters and have been known to use folded paper towelling at a push, that's sufficient filbe no issues with particulates on ptration for replenished developers, fixers. selenium toners etc. I've no issues with particulates on negatives or prints. I do have a lot of lab grade filter papers but they are slow, I've no idea where the coffee filters came from as I've never drunk coffee but they are roughly the same grade as coarse filter papers.

Filtration doesn't need to be particularly fine as chemistry will constantly pick up dust, small fibres, silver sludge during processing.

Ian

John Wiegerink · Apr 15, 2017

mshchem said:
Excellent solution!

I know Gerald might not think it an excellent solution, but it does work for me so I'll keep doing it for now. Plus, I'm a cheapskate!

Gerald C Koch · Apr 15, 2017

bvy said:
I don't get it. If a simple coffee filter works, why do I need lab grade? It's not about economizing for me. Before the coffee filter, there's precipitate. Afterwards, it's gone.

The point of not using coffee filters is that most precipitates found in photography will easy pass thru them. They will not filter out anything smaller than an elephant.

Gerald C Koch · Apr 15, 2017

The other reason to use filter paper and not various substitutes like paper towels is that you are assured that it is "lint" free. That you are not introducing another problem to your solutions.

What you want to get is student grade (think cheap) paper. You don't want ash free or analytical chemistry grade. Get ones marked coarse or rapid speed. If you must use coffee filters there are different quality filters. Some are really poor even with filtering coffee grounds. What you want are flat circular paper not the Mellita little bags which don't work very well as you cannot get a vacuum to speed up filtration.

Finally a word of advice. It has been my experience that once you get crud stuck to film it is very hard or impossible to remove it. Even if you are successful in removing it there is still a mark left.

mshchem · Apr 15, 2017

I have never needed to filter solutions. I have sediment filters on clean municipal water. I use RO water for most ever solution. My question is what are you filtering out and why is it there? Something seems amiss if you are forming ppt. IF I did want to filter, and I wanted to get it clean and fast. Here's a good starting setup. Probably want a dryice bath and a trap flask in between the flask and the pump. In the old days we used dry ice and Freon 11.

Even easier is a little Nalgene aspirator vacuum source that runs of of tap water.

I am by nature not a patient person, Use a thick fiberglass filter and keep the vacuum low. If you turn the vacuum on full you will clog just about every filter. I suppose you could make a centrifuge using 5 gallon pails too. That would be more for a commercial operation. For crying out loud if you want to use a coffee filter, do it. It's fast cheap and if you get some crud, well, it makes you feel good.

Like "pollen catching" furnace filters, it wont make any difference in the outcome but it feels rewarding.

I need to go make sure I still have Helium sparging my Dektol. (Seriously Kidding)

In chemistry, sparging, also known as gas flushing, is a technique which involves bubbling a chemically inert gas, such as nitrogen, argon, or helium, through a liquid. This can be used to remove dissolved gases (e.g. oxygen) from the liquid. By Henry's Law, the amount of dissolved gases in a liquid depend on the partial pressure of the gases exposed to the liquid. Sparging increases the gas-liquid interface.

I love this, I say the more complicated the better!! The really slow paper is ANALytical!

Best Mike

Coffee filters, or Lab Grade Filters?

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