How does a capsule in a toilet work?

Hi everybody reading,

I'm new the science world, and strangely I saw my dad put in a toilet tablet into our cistern system. I dont understand how this sits in water and doesnt react, but then every time we flush it, it does. Could anybody explain please, my dad doesnt know.

Sorry for the lame question.. just found it interesting.



  • These "tablets" are usually one of two types:

    1. A cast mixture of a high melting point nonionic detergent (perhaps stearyl 25-ethoxylate) and a lower melting point ethoxylate such as stearyl 5-ethoxylate. The lower ethoxylate is relatively insoluble in water and gives the longevity, the high melting point ethoxylate enables the tablet to have sufficient "body" to withstand handling. They can contain up to 5% of colorant such as FD&C Blue No1. Often wrapped in a PVA film to protect against colour transfer whilst handling.

    2. A hard pressed mixture of conventional toilet cleaner alkalis or of trichloroisocyanuric acid. This last has a low water solubility and can last several weeks in a toilet cistern slowly releasing its contained chlorine. TCCA is a  VERY POWERFUL OXIDISING  AGENT and must be handled with great care and the manufacture of blocks should only be attempted by specialist manufacturers. It cannot be mixed safey with other materials.
  • We certainly don't want exploding toilets. No sir. (A friend tried to clear his drains by flushing a chunk of sodium metal. The explosion blew a manhole cover in the road into the air, and showered a passing pensioner with the brown and smelly)
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • @johnb incredible. That makes perfect sense. Would I be able to make one at home? Or something similar that creates bubbles and a nice smell to begin with??
  • You could make the coloured ones at home  - if you are able to obtain the ingredients - which may not be easy for you. To be honest, it isn't really worthwhile doing-it-yourself.
  • What would the ingredients be? I should give it a go.

    See I thought it was like making a bath bomb, but more complex. I've actually got some ingredients from bath bombs from a while back.. citric acid, SLS, Sodium Bicarbonate and cream of tartar. Any of them of use??
  • Any of them of use??

    No.  They will dissolve far too quickly.

    I described suitable ingredients in my first reply. Whether these are available to a small user in your country, I don't know.

    Do NOT try to make any of the TCCA products. It is very unlikely that a home user would be able to obtain the materials but, in case you are, heed this warning ver

  • Got you. Is option 1 more than the  two ingredients you mentioned?
    - stearyl 25-ethoxylate
    -  stearyl 5-ethoxylate

    Do these include the bleach that kills bacteria, as well as the chemical to create the bubbles? I guess ultimately thats what a toilet tablets purpose is right?

  • edited December 2016
    A most important part of option 1 is the dyestuff - in fact it is THE most important. These products do little more than provide colour and a slight foam to the water from the cistern. The dilution rate is so vast (just think, a 50gram block slowly dissolving in probably hundreds of litres of water - almost homeopathic in concentration).

    Similarly with the chlorine releasing blocks , they do little more than release a chlorine type odour, the amount of chlorine released per unit volume is miniscule.
  • Hi John, Happy New Year!

    I'm finding this difficult to understand in all honesty. Is there a simplified way you could explain to me what I need to make one please? I'm not quite getting what it is I need or what to do next? Thanks
  • You need to make a mixture of stearyl alcohol (5 or 6)-ethoxylate (this is a soft solid) and stearyl alcohol 25 ethoxylate (this is a hard waxy material). The first item gives longevity to the block, the second the hardness and handle-ability. The more of item one, the longer it will last but the softer it is. That is the reason that some of the longer lasting blocks are wrapped in a water soluble wrapper. The colour is most commonly given by FD&C Blue No1 (CI42090).

    These materials are not commonly available to the home user. Do you have a source of supply? If not, there is little point in me going further.
  • I have found a few suppliers. However, they dont call their items those specific names. For example, I've found a 'fatty alcohol ethoxylate' and 'cetyl stearyl alcohol' (boosts foam, which I'd be interested in doing I think)

    Is this because there are various types of ethoxylates, and depending on the number, it is a different type?? Noticed here

    I also found two UK suppliers, but having searched, believe they only supply the stearyl 5-ethoxylate;

  • Before you actually make this, I suggest you check your cost of ingredients against the cost of buying one in the supermarket . . .
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • As it appears that you are in the UK, stearyl alcohol 21-ethoxylate is available from The Soap Kitchen

    Although not quite 25 ethoxylate, the difference will not be noticed in a product of this type.

    Cetyl stearyl alcohol (or anything similar) will NOT boost foam.

    Please heed the advice from Belassi and from me earlier>
    To be honest, it isn't really worthwhile doing-it-yourself.

  • It's just something I'd like to attempt as a hands on hobby. All of your help is so appreciated as well, looking forward to making it.

    Thanks for the 21-ethoxylate John. That site doesnt seem to have he 5-ethoxylate though.

    Which of these make the foam then?

    You reckon it'll be an easy case of mixing together right proportions then making it into a tablet??

  • The materials are mixed and melted together with the dyestuff.
    Both materials contribute to the foam.
  • Ok great.

    Could you check these for me please?

    FD&C Blue No1 (CI42090 no1 blue fd&PN=fcf-blue-powder.html#SID=47

    Strearyl 5-ethoxylate
    Could you tell me the alternative name if one? As I cant find a place that have this?
  • That is correct for the dyestuff.

    Regarding the stearyl-5-ethoxylate, you already told us that you have a source (Bonnymans or Mistral)
  • Great!
    I'll check again once on my personal laptop. But I believe it was this I presumed was Stearyl 5-ethoxylate?

  • No, that is not the required material.
  • Hi John,

    Finding these aren't easy, but persevering.
    Are there any additional ingredients required for this? Would these ingredients bring in the element of medium thick foam and the cleaning properties?

  • Are there any additional ingredients required for this? Would these ingredients bring in the element of medium thick foam and the cleaning properties?

    The ingredients for a basic "blue block" are as given. Some have had perfumes included but, as the dilution ratio is so vast, these are ineffectual. Similarly with cleaning power. All that can be expected from this type of product is a blue colour in the flush water and some fairly transient foam.

    If you find it impossible to obtain stearyl 5-ethoxylate, it is possible to substitute coconut monoethanolamide (cocamide MEA). This may give improved foaming. It was not used in the original commercial formulations because of relatively high cost. It is available in small quantities from several suppliers.

  • It's proving difficult for those items. stearyl 21-ethoxylate and FD&C Blue are good. But even cocamide MEA is not easy to find.
    Do you have any recommended suppliers? Not looking to buy a tonne however!?
  • I just wanted to let you know that I have just found cocamide MEA, great success (ignore my last post).

    Should I buy that, and the Stearyl 21 which is available and then the FC&D? Would that be ok to make these capsules?

    As I mentioned, I really want to ensure I have a good 'solid' foam from the capsule, and so hope these ingredients can create it. I noticed yesterday, my supermarket bought capsule gives little foam. That's something I'd like to improve on my version.

    Would I also need to purchase the paper wrap? Maybe you could advise on next steps before I purchase so I know what's in store?

    Ever so thankful for your advice and guidance.

  • Those three materials are all you need to make a high quality product. Ensure you have cocamide MEA and not DEA (which has completely different properties.

    You will have to do some experimental work trying different ratios of detergent to check which gives the longest life and best visual effect.

    The dye content is about 2% - 5%.

    Regarding the amount of foam generated, the cocamide MEA is a very good foam stabiliser and will most likely give a superior foam compared to that of a commercial product.

    The steareth21/cocamide MEA block will be much harder in texture that commercial ones and may well not require a wrapper. If you want, you can get a suitable product from Amazon

  • Great.

    I've been sent a data sheet for Stearyl 25, asking if it is the correct type. Are all Stearyl 25 the same? Should I continue with that or the Stearyl 21??
  • The data sheet you sent describes the correct material. It doesn't really matter which one of the two you select - comes down to price really!

    Something that hasn't been mentioned is the process for making the blocks.

    It is simply melting the two detergent materials together and then adding the powdered dyestuff and mixing well. The heating should be done over a waterbath - not direct gas or electrical heaters and do NOT make it in the kitchen. The dyestuff is a very powerful colouring agent in very fine powder form. You may be surprised how easily it can distribute itself and stain everything it touches.
  • Wow, prices are something else!

    Thanks for the heads up.

    Do you have a recommendation on the amount of each product to use? (more cocamide, more stearyl 21??)

    I'll take note and let you know once I have everything. Thanks
  • The ratio of the detergents depends on how long you want the block to last sitting in the toilet cistern.

    The more CME, the longer it will last but the less effective (less colour released per flush). You may want to start with 10 - 15 % CME and test that first.
  • Hi all, hope everyone is well.
    Was hoping if you could help me answer a few more questions please?

    From the items mentioned above, how much foam would they create? I'd like to create maybe 4 inches of thick foam and wanted to ask what could I add to achieve this? There was a previous post about thickening agents and shaving foam, but could anybody advise please?
    Also, with these foam bubbles, what could I add to make them last longer, maybe a few hours at least?? But something that is not going to cause any toilet to block?

    Hope someone could help with these questions!
  • Also, with these foam bubbles, what could I add to make them last longer, maybe a few hours at least?? But something that is not going to cause any toilet to block?
    This is something that you should not do, because it causes problems in wastewater treatment plants, with clouds of foam building up and blowing away in the wind.
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • Hi Belassi, just read about this, from looking at the photos its a horrible thing to happen! 
    What about shaving foam, does that cause an issue, just curious as I use that.

    Do you know if there is an eco friendly foam that fits my needs with whats been recommended above?

    Thanks for bringing that to my attention, unbelievable..
  • I think shaving foam is really a form of soap, so not really anything new there. So, have you tried making some yet?

    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • Shaving soaps/creams/foams are, as Belassi says, based on soap.

    Soap has the characteristic of decomposing before or in wastewater treatment systems and biodegrading - it doesn't then detrimentally affect ecology.

    Your original question was about cistern blocks which I think I answered adequately and in detail after a very protracted series of replies.

    The question you are asking now is about a new concept. This being the case, it is or innovation. Nobody here is a charity and new work had to be paid for. If you are happy to pay for development, fine. If not, it is time to either forget the whole thing or start doing some work yourself.

    A few points:

    1. If you have several inches of persistent foam in the toilet bowl, what then is the point of the cistern block providing colour to the water?

    2. "Eco-friendly foams" and "persistent foams" are a contradiction.

    3. You mentioned thickening agents. These are for totally different products. Be careful not to conflate completely different product types
  • Hey John, hope you're well. You have been very helpful in recent posts and I've enjoyed your guidance. Apologies for the lengthly understanding process, your patience is much appreciated!
    Nonetheless, I've been reading from the guidance you've given me, and searching for the answers to my last post, but haven't had much luck, so thought I would ask here.
    If these questions are no longer open to advice, then please drop me a pm so I can continue with this experiment. Would be great to speak a more fluid conversation.
    Otherwise would love to have some help.

  • Ryoo,

    It's not so much a case of not being open to advice, I think you are venturing beyond your capabilities, especially as your original enquiry was a pretty general one asking how in cistern toilet blocks worked. This developed into the ingredients of the blocks and finally to my seeking out suppliers of suitable products with availability in small quantities for the offered formulations.

    Your current query is not for advice, it is asking for development information for new ideas. This takes time and money on our part and it is a bit much asking for this on a general forum.

    If you do wish to pay for work to be done, there is a section at the top of the home page of people offering development services, although the negatives mentioned in my previous reply still hold true.
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