Mordants, Modifiers, Temperature, Duration and Three Baths - Part 1 - Hot Baths

Comments in bold were written when I revisited this subject after about 10 months....


I have decided to comment on the final quality of all the mordanted yarn in this post, (which was originally intended for hot baths only)....


The pictures only present the hot baths but I have pictures of all of the them and some of the yarn (though I am using it up quickly for the dye uptake experimentation) and if anyone would like to see them please email me...


Please consider these bold comments as my final observations on this experiment, (at least for the time being)...


Again, I would like to stress one point....We were experimenting with delicate, very fine, angora-merino, handspun singles....They are considerably more responsive to all factors then regular machine spun yarns. 


It is my recent work with metallic salt samples and the color yellow that has led me to revisit and try to share the conclusions of this experiment with others.....When I jotted down my thoughts originally on the hot baths, I only had the hot bath results on hand, and all the observations were based on the comparison between hot baths only....


Now I can compare the three baths from the perspective of 10 months of aging and this gives me a clearer idea of the impact of temperature, duration and substances on our woolen fibers...


I have noticed in my postings that I have tendency to get caught up in little details, in this update my observations will be brief. If anyone wants more detailed info about a specific example (and there are over 250 of them) or the multitude of cross-comparisons that this experiment offers please write to me privately.


For first time readers and repeat readers, I would recommend just to scroll down through this post and read the bold text only. It offers the essence of what I have noticed. Originally I wanted to describe every step of this experiment, but that turned out to be impossible...

Three months ago we asked ourselves a question. 'What is the relation of mordanting substances, modifiers, temperature, duration and types of mordanting baths to the resulting fiber quality?'

In order to throw some light on this we ran an experiment with18 different mordanting substances, mordanted in three types of baths hot, vat and solar, with different exposure times.

Some of the answers we obtained were predictable, others confirmed our previous observations, but as always there were a few new insights, some quite surprising.....

Hope that some of you will enjoy this series of posts, and possibly discover some things that we missed in our own observations. If you do, please share them with us.

Let's start with hot mordanting baths. We ran these in the 80°C to 90°C range, trying our best to keep it at 80°C. We used 5 durations: 5 min., 15 min, 30 min., 1 h. and 2 h. Our skeins were 10 g. each, and made of handspun angora/merino singles.

We use a grading system of (1) to (10), where (1) represents the unmordanted yarn and (10) completely destroyed unusable yarn. The best score that a mordanted yarn could get is (2).

Here are the results on 18 mordants, modifiers and assistants. Please excuse some of the spelling errors on the cards.

1. Alum 25%

Solar yarn is by far the best...Looks as if it was never mordanted....It has bloomed, the other two yarns have shriveled. It is also much softer and could easily take a higher concentration of alum.  The hand of the 25% alum is perfect. 45C is a little better than 80C, but both are in a different class altogether when compared to solar.


The difference is huge, and cannot be overstated, the only way that I can convey it is to say that somehow life has been added to the solar fibers and taken away from the other two.


Most of my dye uptake experiments have confirmed that it gives stronger, faster colors than the hot mordants.

No wonder alum is such a popular mordant. There was very little damage to the fibers, even at this high concentration. 5, 15 and 30 min. baths all got (2), the 1h and 2h got (3), because the fibers became progressively harder after 30 minutes, but are still very usable.....This pattern, of a 30 min. limit, will stay with us through the majority of these examples. 

2. Iron 4%

Iron is the first mordant in the list whose change in coloration indicates the rate of uptake. So it threw some light on the other questions that I have been considering while running this experiment on fiber quality...The first of these is mordant uptake in the different baths and durations...In a nutshell, the 45C, vat style method, is generally worthless (and from now on I will stop commenting on it). While the hot and solar both show very good uptake results, through the reddish blush on the yarn, the vat style bath gives us a dirty white at best....


Even thought iron is harsher than alum the differences in fiber quality remains the same as with alum and solar trumps again.


The hot mordanted yarns gave me slightly stronger color  (the difference is minimal and negligible) than the solar ones....Since the fiber quality gap between the two methods is so huge, I can easily double or possibly even triple the amount of this mordant in the solar baths, and still get a better fiber.


(As a side note, all of my fibers from last year at higher iron concentrations are holding up well). Presently I feel that the method of iron application (and specifically the temperature) might have more to do with the fiber damage than the concentration of the mordant. (All of this has to be tested of course).

Iron is the first of our mordants that leaves a color trace of its absorption, but there will be many others. First of all very little damage at this rather high concentration of 4%. The idea of using iron at even higher concentrations is more and more appealing to me. Even though the 1h and 2h yarns were slightly harder, all of them got a (2) rating, with the exception of 2h which showed a bit of shrinkage as well (3). It is worth pointing out that each color (absorption) is progressively deeper. Though the 1h and 2h almost look the same.

We also noted uneven coloration in the 5 and 15 min. batches. This is all our doing, we did not move the wool around enough. This is very important esp. in the case of hot baths of short duration, but as it will become evident later, in case of any bath, whatever the duration

3. Copper 4%

The hot baths look mutilated in comparison to the solar. The hand and fiber quality in general is similar to iron, both not quite as soft as alum.


The biggest surprise here is that solar baths show better uptake than the hot ones. In this case I am basing myself on the color of the mordanted yarns.


(On the same note, I added this observation later: with certain mordants such as copper, iron and the organics, the color intensity is a good indicator of mordant uptake. Solar copper yarns, and organics for that matter, gave me better color results, in actual dye baths, than the hot mordanted yarns.)

The effect of duration on absorption makes itself even more evident with copper. In this case each batch is considerably deeper than the previous one. But our angora does not take to copper well in a hot bath. As can be seen in the picture the fibers are progressively more damaged. 5 and 15 min are still soft, but 30 min becomes hard and 1h and 2h are very hard and quite destroyed. 1h and 2h show strong discoloration, this is again a good reminder to move those fibers gently around in that bath. Please note the shrinkage and fiber damage.This was one of our worst hot baths. The final scores 5 min and 15 min (2), 30 min (3), 1h (8) and 2h (9).

4. Tin 8%

The solar baths are still better than the hot ones, but the divide between the two is lesser than observed in the previous examples.


Basically tin holds up well at 80C. I am quite surprised by this result.


The hand is similar to iron and copper.


After a few tests with dyes. Tin was the only exception where the hot bath mordant gave me a clearly better result than the solar, esp. with yellows. 


Of all the mordants and modifiers that I have tested, this is only one for which I would recommend the hot method. Personally I am still not sure if I will ever use it for dyeing, but if I do I will experiment with a higher solar concentration before I use the hot method approach.

Tin which manifested such negative impact on our local wool works very well with angora and merino blend. This is what we noticed before but were happy to reconfirm t in this experiment. The overall results and fiber quality are similar to alum. 1h and 2h show a little hardness and fiber damage, they get a (3). The rest gets a (2)

5. Chrome 4%

Again, hot baths are mutilated as compared to solar....I am starting to believe that what I considered a surprise in case of copper is actually a rule....Solar baths offer much better mordant uptake.

We are aware of the issues surrounding these toxic mordants, but decided to include them for two reasons. The first is to find out whether they are necessary (and have been too hastily set aside), or can be replaced by other mordants. The second is, what is developing to be my personal fascination with older dyeing texts. I wanted to experiment with tin and chrome and others in order to better understand the writers of these older texts. We are very careful, with the mordant bath and rinse water and recycle it all.

Chrome was a pleasant surprise and gave identical results to alum and tin. One point of note with chrome is the progressive color change which is evident up to 30 min and stops there.

6. Zinc 4%

Similar to, but slightly better fibers than chrome. 

In general chrome, zinc and tin damage our fibers slightly more than copper and iron, and chrome is probably the worst culprit.

Here is a basic list of the effect of solar metallic salts on the fiber structure of our angora/wool blend....Alum is best, followed by iron, copper, tin, zinc and chrome...Differences are gradual and all solar yarn is in acceptable condition, and generally much, much better than the hot and vat yarn.

Zinc behaved well in all baths. Same results as alum and tin. 

7. Tannic acid 10%

The results on all acidic baths, were good. Very little fiber damage. Much less than most metallic salts, with the exception of the solar alum.


All three baths are decent, solar is best from the point of view of fiber quality.

Tannic acid is another mordant expressing very limited fiber damage. All the batches were soft, with slight hardness at 1h and 2h. All got a (2) with the exception of 2h which got a (3). Progressive color change up to 1h, where it seems to level off.

8. Oxalic acid 10%

The discoloration, described below, only happened in the hot bath. The solar bath left excellent fibers.


With oxalic acid and few other substances listed directly below, we stepped away from traditional mordants 

and looked into the action on fibers of substances which are generally used as assistants or modifiers.

This is another chemical which showed significant fiber damage, esp. at 1h and most definitely at 2h. Granted, 10% was way too high and in the future we will bring this down to the 2%-4% range. 

The 5min, 15min and 30min baths were all soft and received a (2) rating. Things changed drastically at 1h, and continued to deteriorate in the 2h batch. Those two received a (8) and (9) rating respectively. As opposed to other coloring mordants where the color concentration changed gradually, the change with oxalic was sudden and started after 30 minute exposure. From that point it progressively got worse. I interpret the sudden change as a physical effect on the fiber structure, a burn or something along those lines. If any one has other thoughts on this I would be interested in hearing them. Since this happened only in the hot baths, this acidic ph threshold is closely related to temperature.

9.  Citric acid 10%

Excellent fiber quality on all three baths, but solar is still best.

This one was lovely and behaved ideally at all durations (2), with slight hardening at 2h (3). Probably our best acidic modifier.

10. Cream of tartar 10%

Excellent fiber quality on all three baths, and, at a risk of sounding like a robot, solar is still best.

Very good results, similar to citric with slightly stronger fiber stiffness at 1h and 2h. All received (2), with exception of 1h and 2h, a (3).

11. Sodium carbonate 4%

As expected, there is more damage to fibers with basic modifiers than with the acidic baths. 


And again (sorry for repeating this so often, but the facts don't lie) the quality of the solar fibers is much higher than that of hot mordanted fibers.

Again, good results. 5min, 15min, 30min, received a (2), slight fiber stiffness at 1h and 2h (3). All yarns still very usable.

12. Sodium bicarbonate 4%

Much more damage to fibers than carbonate. 


Solar yarn shows fullness and a certain bloom, white the fibers of the other two baths have thinned out, as if eaten away. Same observation applies to sodium carbonate.

The bicarbonate behaved slightly better than the carbonate, but the difference was minimal. All got (2), with exception of 2h which received a (3).

This is it for modifiers and assistants. In retrospective I wish we tested a few others, and will probably do so in the near future.

13. Pomegranate skin 100%

Great fiber quality in all organic baths, comparable to solar alum. 


...Again, just as you are expecting solar is best.....

With pomegranate skin we enter a new world. A strange place that is hard to define. This one and the next five substances can be described as dyes, or organic mordants, or bases for over-dyeing, and they are all of that.

Out of all the substances we tested this is the group that showed the most interesting variations with temperature and duration. I hope this becomes evident during the next few blog posts.

Very little negative effect on the fibers. They are all very soft (2), with exception of 2h which shows slight stiffness (3). There is a progressive change in color, hence absorption throughout the 5 exposure stages.

14. Ravenchini 100%

I discovered this dye last year and absolutely love it...


Fiber quality is significantly better on solar than on the hot baths.


The brightness of the solar colors is overhelming...


...This brings me back to what I said about the alum baths, there is something inherently sad about the hot bath fibers when they are compared to their solar counterparts....


...When I look at this difference, I cannot help asking myself : are we throwing a lobster into a hot water bath, when we treat protein fibers in this manner ?


I will stop my comments here for two reasons, expressed in three points :


1. The same story weaves itself into the other organic mordants....


2. Solar is better.....


3. I am not yet convinced about the usefulness of organic mordants. I can see using some of them as dyes, but can usually get a similar or better palate with copper and iron and ph manipulation.....


...Actually, this was the low point of the whole experiment....


I started it out of concern for my handspun fibers and for cashmere spun by any method....There were really no expectations as to obtaining specific results, and never would I imagine myself a solar purist, which this experiment has turned me into.

In retrospective, deep inside, I had one hope, and that is that the beauty of organic mordanting would reveal itself to me.....It has not, so far it eludes me, just like the color black on wool.....(Would it not be funny if these two were closely related?)....


...But having just said that, and knowing how my crazy mind works, I have a feeling we will revisit the world of organic mordanting soon.....They offer great fiber quality, on par with alum, so I really need to look at them closer....


...but first......the enticing world of solar dyeing beckons.....

Since our rhubarb plants did not make it this year, we set out to find rhubarb in dried form. We were able to obtain two species of herbs which are supposed to be rhubarb this is the first one of them. I am posting this one with a bit of hesitation, since there was lots of confusion as to the Latin name. Equipped with my reference texts, I will do more research on this one in September. For the time being please accept is as rhubarb, with a grain of salt and an open mind.

Very little negative effect on the fibers. They are all very soft (2), with exception of 1h and 2h which show slight stiffness (3). Just as with pomegranate and most of the organic mordants there is a progressive change in color, hence absorption throughout the 5 exposure stages. I suspect this pattern will continue with most dyeing plants.

15. Amlavetas 100%

This is the other plant, which is supposed to be a species of rhubarb. I am not at all convinced, but will research it further in September. Please refer to my comments above in  #14. In any case the colors are nice, hope they hold...

Fiber quality was the same as with the rhubarb above, In general very good. Color concentration or absorption peaked at 30 minutes.

16. Myrobalan 100%

In general not bad, but the fibers were a little harder than with the previous organic mordants. The uneven color with serve as a good reminder to turn those yarns well during mordanting and dyeing. Conspicuously, there is very little color difference between 15min and 2h. All got (2), but 1h and 2h received a (3) and (4) respectively.

17. Aamla, Indian gooseberry, Phyllanthus emblica

One of the most important Indian organic mordants, behaved quite well throughout and showed progressive color changes with each exposure duration. All batches received a (2), with 2h getting only a (3). Still they are all quite usable.

18. Walnut bark

Good progressive color change, peaking at about 1h. Same results as for amla above.


There are quite a few organic mordants missing from this list. We will look into them in later tests...

This is it for hot baths. I hope to describe the vat and solar/moon baths in later posts.