April 2021 Soap Challenge Club: Polka Dots

The April 2021 Soap Challenge Club challenge was to create symmetrical polka dots in soaps using straws, soap dough, or some other shape that goes throughout the soap.

I am competing in the beginners category. This means my shapes have to be round cylinders. The tutorial used plastic straws and a template made with a hole puncher. I decided to use wooden dowels, as the selection of straws in my local markets was limited.

Materials:

  1. Wooden Dowels of varying diameters
  2. 3D Printed Template: upper and lower plates
  3. Clear acrylic mold (mould)
  4. Soap recipe (oils, lye, micas, essential oils, sodium lactate)
  5. Oven for cold process oven processing (CPOP)
  6. Pipettes (preferably with a long thin tip)
  7. Melt and pour soap (to set the 3D printed templates)
  8. Miter box and chef knife, and planer.
  9. Additional round, oval, “rock shaped”, or other individual mold (optional)
    • Used to rebatch the scraps from this method (a fair amount of soap scraps or “waste” will be generated).
    • It is also possible to hand mold rock shapes or use any available molds. The point is to reduce waste and use available resources.

I was happy to find a small company Woodpecker Crafts selling these for a reasonable price and the shipping. https://woodpeckerscrafts.com/dowel-rod-pack-12-assortment-40-pieces/

Method:

  1. Acquire wooden dowels of varying diameters
  2. Design 3D printed upper and lower plates (template) for mold
    • Diameter of opening should be designed to fit wooden dowels
    • The lower plate should be designed to fit inside your mold of choice
    • The lower plate has a tighter tolerance to ensure a tighter fit of the dowels
    • The upper plate has a looser tolerance to allow the plate to slide through the dowels (to be lifted as needed)
    • The upper plate should be wider than the lower plate
    • It is recommended to test your 3D print fits your dowels before proceeding
  3. Place bottom 3D plate
  4. Pour a thin layer of melt and pour soap in the mold to set the bottom plates and ensure they don’t move around in the mold
  5. Insert dowels
  6. Pour another thin layer of melt and pour soap to cover the top of the 3D printed plate to avoid contact with caustic raw soap batter (this may or may not be necessary depending on the 3D filament used)
  7. Add top plates to stabilize the position of the dowels
  8. Mix up base soap and pour into mold
  9. CPOP base soap overnight
    • Preheat oven to lowest available setting
    • Turn off oven and let cool slightly
    • Turn on oven light
    • Insert soap and leave overnight. (I have read 6-8 hours may be sufficient).
  10. Remove soap from warm oven and let cool
  11. While the soap is cooling, prepare the soap used to fill the holes.
    • It is recommended to make extra amounts, as it may be needed later to fill any gaps in the holes, and to ensure uniformity.
    • Mix soap to emulsion only
    • It may be desirable to only mix the micas with the soap as you fill that diameter hole.
    • Ensure the micas are mixed into the soap to a thin trace. You want a very liquid soap to flow in holes, but you don’t want the micas improperly mixed.
  12. Slowly remove wooden dowels
    • Recommended to twist the dowels prior to lifting the dowel out
    • Depending on your setup, it may be possible to see through the bottom of the acrylic mold through the hole.
    • Occasionally a small amount of soap collapses into the hole. I used a straw to remove the occasional bits of soap crumbles that fell into the holes. (Any hollow rigid cylinder with a the same diameter or slightly smaller diameter than the thinnest dowel will work)
  13. Fill the holes smallest to largest.
    • It may be helpful to have a picture of the template out to ensure you don’t mix up the different colours.
    • You may notice sometimes when filling a hole a small amount of the soap batter will seep through to the bottom of the mold or into the other holes. Don’t despair as you will be removing the bottom layer of soap.
  14. Once you have filled all remaining holes in the soap, the entire loaf goes through the CPOP process again.
  15. Remove soap and let cool.
  16. Remove from mold and remove bottom layer of 3D printed plates and melt and pour soap. Save soap scraps.
  17. Cut, plane, and bevel to personal preference. For this particular design, it is recommended to leave some soap base around the polka dots to create the most uniform looking bars.
  18. Rebatch soap scraps (all the cold process (cp) and melt and pour (mp) scraps can be rebatched together) into soap stones. See method here: https://www.thecuriouslycreative.com/soap-making-guide-rebatch-method/

The Experimental Write Up:

This month’s entry must be done in a slab or loaf mold. I only make soap as a hobby so this soap will most likely end up being a gift, so I need it to be as universally appealing as possible. I decided to make a vegetable oil based soap scented with essential oils.

I needed precise placement to achieve anything symmetrical. I used a 3D printed upper and lower plates to hold the dowels.

3D printed plates
I was short a few dowels and had to cut some in half. If I were to make this style more often, I would ensure each dowel was long enough that I could slide the top plate all the way to the very top of the dowel, to allow better access to the mold.

The upper plate is slightly larger to rest on the edges of the mold, and the holes have a greater tolerance than the lower plates to allow the dowels to slide more freely on the dowels. These were designed to fit on the standard loaf soap mold, but switched to a clear acrylic mold for better visibility.

To reduce movement of the plates they were adhered to the bottom of the mold with melt and pour soap. I was worried the soap would eat into the plastic (not rated for highly alkaline environments), so I covered the plates with another layer of melt and pour to protect the plastic (and my soap entry!).

I mixed up the base soap (30% RSPO Palm oil, 45% Olive Oil, 25% Coconut oil, 5% superfat, water 32% of oil, 2% sodium lactate, and 5% essential oil blend of peppermint and tea tree), preheated to the oven (170F/77C), inserted the soap and turned off the oven, turned on the oven light, and left the soap overnight (CPOP).

The top of the soap looked grainy coming out of the oven. Clearly 2% sodium lactate (of oil weight) might work beautifully for my personal use recipe, but was far too much for this vegan recipe. Determined to see it to the end I started removing the smallest dowels first and filling them slowly ensuring my stream of liquid soap was ~25% the volume of the hole to allow air to escape.

Two dowel sizes removed and filled

As I progressed, when I removed the larger dowels they created a suction which pulled some of the fluid soap from the previously filled holes to the bottom of the mold. So I decided to remove all of the dowels and move on. The soap was placed back in a warm oven to set the polka dots.

All dowels removed and two categories of the dowel sized holes filled.
Soap filled and CPOPed a second time

First thing to do was remove the plates and melt and pour soap from the bottom of the mold. The beautiful contrast between the fluorescent colors and white melt and pour, and the dull color of my base color had me really unhappy with my color choices.

The white background really makes the bright colors pop! You can also see here that the base soap was grainy and probably should have been left longer to cool.

Next up the cutting and trimming of the soap. As a home hobbyist, I haven’t invested in the high quality tools necessary to give me clean even right angle cuts, professional looking beveling, etc. Cutting the soap became a frustrating study in diminishing returns. All around I wasn’t truly happy with the soap (crumbly, background color turned out different than intended, poorly cut, white halo in center of soap, etc).

I really did like the overall design. I felt the design deserved another chance, another color scheme, and a new fragrance blend to match. It’s my personal opinion that color choices can make or break art. I found a spring color scheme online that was based on a picture of flowers. It was outside of my normal range of color choices, but seemed fitting for the design. I chose a new essential oil blend of lavender and geranium. I wanted to have a white soap base this time, with some gorgeous pinks, and a touch of green. After an unscientific polling, it was decided to use green as the background color. 🙂

5g Mica samples from Nurture Soap, top to bottom
(Alpine Green, Oleander, Love Song, Lollipop)

The process and recipe was the same as the first, but only 0.5% sodium lactate was used this time. I also removed all wooden dowels before proceeding. The second time the dowels were a little harder to remove, so I had use a tool to grip and twist a few out of position. The dowels do wick liquids from the soap but seem structurally intact after two uses.

The green floral soap with all dowels removed. If I were to redesign this, I would increase the space between the center hole and surrounding holes, as it did make this design fragile.
The soap filled with polka dots
after setting up in the oven

Of course there was still plenty of room for improvement after the second batch, but the soap was a proper consistency, the scent was heavenly, and the design pleasing. I considered doing one more iteration, but was worried about the volume of soap scraps this design produced and what I would do my surplus soap bars. 😅.

My first batch being so crumbly created a lot of soap scraps. To be frugal, I mixed scraps from the first batch (cp and mp combined), and rebatched them in the microwave with ~10% water (weight compared to soap scraps) & ~5% oil (why not?) and made my most convincing rebatched soap stones yet.

Minty fresh rebatched soap stones

4 thoughts on “April 2021 Soap Challenge Club: Polka Dots

  1. Excellent write-up! I enjoyed reading about your successes and improvements! You did a great job with your second batch – I believe the reduced sodium lactate and brighter contrasting colors really give a much better result! Congratulations!

    Like

  2. Firstly your soaps are stunning! I love the colours in both attempts and your explanation of your experience is really through! Super execution🤩

    Like

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