Borax and Sunlight soap.
Thin waxy film coating a 3lb tumble barrel – unexpected and rare, from the use of Sunlight soap.
Borax mixed in with grit for a tumble, keeping the grit in suspension. 400 grit tumble in a 6lb barrel.
My detailed illustrated instructions for tumble-polishing are to be found in the Series “The Seven Stages in Tumble Polishing Stones”, written in 2017-2018. As noted there, I use soap in the process of tumble-polishing in two ways, in a wash tumble following a grit tumble, and as a burnishing tumble after the polish stage.
So, first, at the completion of a grit stage, after I open the barrel, I run water over stones to remove the slurry. I then put the stones in a “wash tumble”, adding a few flakes of grated Sunlight soap to fresh water in the barrel. Sunlight soap does not contain any chemicals likely to cause problems, like the production of gases, and it gives rise to enough suds but not too many. This wash tumble stage lasts for a few hours, getting rid of any lingering tiny amounts of slurry or grit from the stones and barrel. The water is usually quite dark and dirty looking after this tumble, so it is an effective clean-up. Other soaps, such as Lux and Ivory flakes, can be used for this purpose, as they are also seen as mild and low-sudsing, gentle, not containing strong or harsh chemicals.
When I first learned to tumble polish, the guidelines I was following said to use Sunlight soap, so I did. It seems to be effective and I haven’t yet changed that practice. I also personally like the link between Sunlight soap and the Isle of Lewis in the Scottish Hebrides. I visited Lewis in 2017, being especially interested to see the Callanish standing stones – see here for an account of that visit. Later, reading about the history and culture of Lewis, I discovered that in 1918, the Englishman William Lever (later Lord Leverhulme) bought the island (actually, the northern part of the island of Lewis and Harris, see map below). Lever had made much of his fortune by the selling of Sunlight soap since the mid 1880s, one of the first soaps to be made from vegetable oil. He was the first to sell soap in individually wrapped bars. As the packaging label puts it these days, Sunlight soap was an early pioneer of “modern mass production, marketing and advertising”. Lever proposed a number of reforms for his newly acquired Isle of Lewis, including doing away with the traditional crofting system, a move strongly resisted by the population. Roger Hutchinson’s book, “The Soap Man: Lewis, Harris and Lord Leverhulme” (2003), tells the whole story in detail. Lever died in 1925, Lewis was sold, but Sunlight soap remained.
Grating Sunlight soap for use in a tumble barrel.
Cover of 2003 book.
It is not always easy to find Sunlight soap to buy, though some supermarkets still stock it in New Zealand. You also have to grate it as not much is needed in each barrel. Furthermore, it contains palm oil which is not seen as an environmentally friendly product. As the World Wildlife Fund puts it: “Large areas of tropical forests and other ecosystems with high conservation values have been cleared to make room for vast monoculture oil palm plantations. This clearing has destroyed critical habitat for many endangered species—including rhinos, elephants and tigers.”
The second way I have used soap in the process of tumble-polishing relates to borax (also known as sodium borate). After each polish tumble, I add some borax to fresh water for a “burnishing” tumble, lasting a few days. Again, this was something included in some of the tumbling guidelines I located when I started. Note that some tumblers are abandoning the term “burnishing” for this stage as they associate it with a dry process, not a wet process. However, the core meaning of “burnish” is to polish and I believe it can be used cover a range of processes.
Bought from Mitre10.
Information that came when bought online.
Borax is sold as a white powder that dissolves easily in water. It has been used as a detergent, a food preservative (now banned for this use in some countries), an anti-fungal compound, a weed killer and a low-toxicity insecticide. It is used by tumble-polishers because again it is a clean soap, lacking perfume and other additives. I initially bought it in 1kg containers from Mitre10 (see photo above) but more recently bought it in a larger lot online somewhere.
This Post reports on a minor unexpected issue with the use of Sunlight soap and an additional use for borax in the tumbling process.
The Unexpected Issue with Sunlight Soap: I had the unsettling experience a few days ago after using grated Sunlight soap on some softish limestone pebbles from Marlborough. I had tumbled the stones in 600 grit just to get the surface clear of weathering and dullness, then did my usual follow-up wash in Sunlight soap. Opening the barrel after that wash, I noticed that the slurry was thicker than usual but also that the usual soap bubbles/suds were not there. After emptying the barrel, I saw there was a thin layer of wax on the rubber surfaces of the barrel and lid.
On the left is the wax coated lid, on the right is a clean lid.
Scratching the waxy coating away.
On the left is the wax coated 3lb barrel.
The limestone stones, many with trace fossils, that had been tumbled in the Sunlight soap.
The limestone stones tend to feel quite waxy after tumbling – you can see the water beading on them in the photo above. But I am guessing that the waxy layer came from something waxy in the soap, and the interaction with the limestone somehow separated it. Maybe. I wasn’t sure what to do about removing the waxy layer. I started to scrape it away but that was going to be a long and tedious process. Fortunately, I found that the next use of 600 grit in the barrel removed all the wax and it did not seem to interfere with its effectiveness for that tumble. So if you discover a thin waxy layer in your barrel under similar circumstances, don’t panic.
The Additional Use for Borax: I have seen in a handful of places online recently that people think the addition of borax to a grit tumble will increase the effectiveness of the grit. Chrissy who writes the excellent “Tumble and Polish” blog, and Nicola who has a rockhounding and rocktumbling Facebook Page, are two New Zealanders who have adopted this technique. One source that especially grabbed my attention was a Post in the Facebook Group, “Amateur Rock Tumblers Worldwide”. There, on 18 June this year, Randy D. Dreenen reported on an experiment to test this idea. He ran two barrels with identical stones and grit, but he added a tablespoon of borax to one. As noted in the photos below, the one with borax in it had a foamy slurry which carried the grit in suspension.
He argued that the stones would come into contact with the grit much better as a result. Randy also examined the grit in the two barrels at the same stage, and this showed “the Borax barrel had ground faster, as the grit was more worn”.
I’ve done more some searching online and found that the idea of using borax in this way has been around for some time. Furthermore, it is argued that it makes it much easier to clean the barrel afterwards. For example, this October 2022 YouTube clip ask “Does using borax during the tumbling cycle really work?” (see photo below) and compares two seven-day cycles with 46/70 grit. The following “Outcome” was noted: “The weekly barrel clean up was a breeze when using the Borax. It also helped to break the water tension (we have hard water) creating a thicker slurry giving us a better grind during the cycle.” And some people have also been using borax at the polish stage. All this hadn’t registered for me until I saw Randy Dreenan’s Post.
So I decided recently to try using borax in grit tumbles to see what the difference was for myself. I have done a handful of 3lb barrel tumbles using three tablespoons of grit and one tablespoon of borax instead of just the usual four tablespoons of grit. I’ve also done a couple of 4lb barrel tumbles using five tablespoons of grit and two tablespoons of borax instead of just the usual six or seven tablespoons of grit; and a couple of 6lb barrels using six tablespoons of grit and two tablespoons of borax instead of the usual eight tablespoons of grit. My aim at this stage has been to observe the frothing within the barrels, how easy the barrels clean up, and whether I can see any downsides.
A 6lb barrel that contained 6 tablespoons of 400 grit and 2 tablespoons of borax. After 7 days tumbling.
I found that the slurry is indeed more frothy with the addition of borax (above right is a photo of a 6lb barrel I added borax to) and that this is likely to increase the effectiveness of the grit. This offers the opportunity to complete tumbling stages in shorter times, say in five days instead of seven, or in seven days instead of ten. The tumbling period can vary with the type of stones and the amount of grit, the aim being to use up the grit each time. I have tried shorter times, by one or two days, and have not yet seen any grit remaining in the slurry. I will continue to experiment with how much grit and borax I use and how long I will tumble for.
It has also been noticeable that the stones and barrels have been easier to clean. Pouring water over them removes the slurry more quickly and more thoroughly. I am still following up with a Sunlight soap wash for a few hours and so far the water has come out dirty, indicating the need for this before going onto the next stage. I have seen some people deciding to abandon the soap wash, but I’m not inclined to do that.
The method for tumble-polishing stones has developed and changed over time (see photos from rocktumbler.com above). New materials are being used, new ways of doing things are trialed, more environmentally responsible guidelines are developed, and people are always trying new things out. There are new ways to improve and to avoid mistakes.
All of this is to be expected and encouraged. Some people are braver, more experimental, more willing to try new things. I tend towards the conservative side, I like to stick with what works for me, but I am sometimes prepared to change, especially when I can see the advantages.
