Shower steamers: the chemistry behind ?

[CecileBC]

Does anyone know if adding salt makes them harder ?
A lot of recipes contains Epsom salt, which "seems" to make mine harder, but without knowing for sure whether it is the salt that is at work there... Epsom salts may make sense in bath bombs because of benefits on the skin, but in a shower steamer ? My current recipe contains those salts, but I may do without them if they do nothing for the binding and hardness.

I agree about the weather being a big factor ! It's a rainy march here in France, and I have had two failed batches this week - and a moonpress broken for applying too much pressure to force them to stay together - and a bad elbow

 

[Becky1024]

Hi !

I would be interested in understanding the chemistry behind shower steamers:
is it the bonding between citric acid and baking soda, packed together firmly with a binding agent such as rubbing alcohol or witch hazel, that creates a new chemical structure that is rock hard ?
Does it mean that the 2:1 ratio between baking soda and citric acid has to be respected if one wants to make the structure rock hard ?

I have tried numerous recipes, and I seem to find that the 2:1 ratio gives the best results in terms of hardness.
However, I would like to decrease the fizz effect, so I have tried less citric acid and have added either cream of tartar or a clay to my steamers.
It turned out that none was ever as hard as the ones made with a 2:1 baking soda/citric acid ratio - and some of them totally crumbly!

Thus my question to try and understand the "chemistry" that happens in the process.

Thanks !

Hope I can explain it clearly! It's pretty interesting to me because I'm a chemist. When you are mixing the ingredients to make steamers, citric acid and baking soda will start react together with the water in your liquid. Rubbing alcohol for example is 70% alcohol + 30% water. Witch hazel contains more water ( I believe it's about 15% alcohol + 85% water). When the reaction takes place the products are carbon dioxide and sodium citrate (a salt.) The sodium citrate salt forms a crystal and that is what makes the steamer rock hard. The key is you want just a little bit of the reaction to take place so that is where the amount of liquid and ratio between baking soda and citric acid come in. You in effect want a nice big hard crystal of sodium citrate with the remaining citric acid and baking soda trapped inside the crystal once it dries.

The 2nd part of the reaction takes place when you put the steamer in the shower and let the water hit it. The crystal structure dissolves, and the remaining citric acid + baking soda react together. The fizz is carbon dioxide escaping.

I have had batches that totally crumble and then have had to use them up a bath salt. I think what is happening is that the ratio is off so instead of forming a big crystal, the sodium citrate forms lots of little ones and then the steamer does not hold together.

 

[Becky1024]

I find that the weather when I'm making steamers can have a big effect on them as well. I'm in the PNW where rain is a constant this time of year, and the high humidity tends to make it more difficult to get a hard bar that stays together.

I've found that too. I cannot make steamers when it's raining outside, even if the AC or furnace is on and the humidity is controlled in my house.

 

[Mobjack Bay]

@Becky1024 Your explanation makes sense to me and perhaps explains why using 91% isopropyl, which is what I’ve been doing, is not the optimal way to get perfect steamers. I assumed that “damp” with 91% alcohol instead of witch hazel (85% water) would be a plus, especially since there is so much focus on keeping the citric acid from overreacting during the making. Maybe my steamers just need a tad more water to help with crystal formation. As for the weather factor, unless makers are keeping ingredients in a dry box, the water content of the dry ingredients will fluctuate a bit as the weather changes, as will rates of evaporation/drying. If success is dependent on crystal formation within the steamer or bomb, then it seems like there are a bunch of ways for things to go off track. I’m looking forward to more experiments.

Thanks for your clear explanation!

 

[Becky1024]

@Becky1024 Your explanation makes sense to me and perhaps explains why using 91% isopropyl, which is what I’ve been doing, is not the optimal way to get perfect steamers. I assumed that “damp” with 91% alcohol instead of witch hazel (85% water) would be a plus, especially since there is so much focus on keeping the citric acid from overreacting during the making. Maybe my steamers just need a tad more water to help with crystal formation. As for the weather factor, unless makers are keeping ingredients in a dry box, the water content of the dry ingredients will fluctuate a bit as the weather changes, as will rates of evaporation/drying. If success is dependent on crystal formation within the steamer or bomb, then it seems like there are a bunch of ways for things to go off track. I’m looking forward to more experiments.

Thanks for your clear explanation!

Monaco Bay thank you for your kind words! You are so right there are a bunch of ways they can go off track. I had a HUGE problem with the wet mixture swelling in the molds starting in September 2022 just as I’m making tons for my Christmas markets. I tried everything- new lots of baking soda and citric acid, alcohol vs witch hazel vs water, talked to the suppliers, etc. I never found the root cause which bugs me. I ended up reducing the amount of citric acid last summer and so far that is working ok.

 

[benjaminandrewc]

Hope I can explain it clearly! It's pretty interesting to me because I'm a chemist. When you are mixing the ingredients to make steamers, citric acid and baking soda will start react together with the water in your liquid. Rubbing alcohol for example is 70% alcohol + 30% water. Witch hazel contains more water ( I believe it's about 15% alcohol + 85% water). When the reaction takes place the products are carbon dioxide and sodium citrate (a salt.) The sodium citrate salt forms a crystal and that is what makes the steamer rock hard. The key is you want just a little bit of the reaction to take place so that is where the amount of liquid and ratio between baking soda and citric acid come in. You in effect want a nice big hard crystal of sodium citrate with the remaining citric acid and baking soda trapped inside the crystal once it dries.

The 2nd part of the reaction takes place when you put the steamer in the shower and let the water hit it. The crystal structure dissolves, and the remaining citric acid + baking soda react together. The fizz is carbon dioxide escaping.

I have had batches that totally crumble and then have had to use them up a bath salt. I also send these details to a popular carpet cleaner at this website and I think what is happening is that the ratio is off so instead of forming a big crystal, the sodium citrate forms lots of little ones and then the steamer does not hold together.

Thank you @Becky1024 for detailed explanation, i was searching for similar and found this thread. once again thank you for your time.