Cheaper Stronger, Better

I have a tendency to be messy, and find the baggie system works best for me when using adhesives. I also have had a preference for polymer adhesives, such as Soudal, over cement-based adhesives, even though these can be messy. I realised I was was scared of cement-based adhesives (CBA)!

Now we all know that different adhesives suit different applications. I don’t particularly like using polymers on stone: it can stain some paler slates; won’t adhere to gritty sandstone; and whilst it works on river rock, can also stain some of them. I have also heard, anecdotally, that it sometimes can peel off Thermasheet/Wedi/Marmox (insert preferred brand name here).  I was also of the view that, as a retailer of a wide-range of product, I should be equally at home with them all, so embarked on a mission to “fall in love” with CBA (thinset to our American friends).

Talk to the experts!

I was concerned that my CBA was going off too quickly, and was too hard to use with the baggie system. (NOTE: I had been using my dry adhesive with the additive that I sold as a bundle). So I contacted my supplier and spoke with the product developer. He designed the batching equipment that makes the product, and is a co-owner of my Supply company, and just happens to be an Industrial Chemist. Here’s what I found out:

1. Deformability (denoted by the S prefix), refers to the capacity of a hardened adhesive to be deformed by stresses between the tile and the fixing surface without loss of adhesion. Deformability is classified into two classes: S1 – deformable and S2 – highly deformable. Tests show how flexible the adhesive is. Flexibility in adhesives improves resistance to impact, environmental stresses caused by temperature and moisture cycles and thermal expansion and contraction in substrates. Simply put, S2 is stronger and more flexible than S1.

2. Many adhesives used by mosaicists are rated S1 (Laticrete 254 is for example, and I suspect Dunlop Tile-All may be). These may be strengthened by the addition of a Latex additive, and some are even bundled for sale with it, which obviously incurs more cost. The adhesive I sell is rated S2.

3. S2 adhesives do not require any additional latex, and should be mixed with water only.  In fact, mixing with an additive reduces work time considerably, and makes them nigh on impossible to pipe through a baggie (yes I have had exploding bags!).  Sure, if you want to mosaic a HEAVY traffic area (driveways, or a spa etc), they are ideal – but should be applied in smaller sections (approx. 1m² max.) with a notched trowel.

That was the answer!

Findings

I am now advocating the use of my CBA WITHOUT any latex additive. Game changer!

The resultant mix is soft and creamy (known as “fluffy” in the building trade), and works beautifully with my mosaic baggies. Feedback on my baggies (and personal experience) is that they form a lovely long cylinder that fits well in the hand, they are strong, and when combined with the reusable silicon ring ties are really non-messy (music to my ears).

The open time on my adhesive is listed as 25 minutes (at 23 ºC). This applies to the building trade, where the normal application method is via a notched trowel. Once the product has ‘skinned over’, it’s no longer suitable to be worked, and should be removed, and fresh adhesive applied.

Pot (Usable) Life is the time a mixed adhesive remains workable after being mixed.  For this product it is 90-120 minutes (depending on ambient temperature). However, I find the product stays usable for a much longer when used with my Mosaic Baggies, due to the fact that they create a sealed container, and the product is air-cured. For example, I recently mixed up 2 batches (approx. 3 tablespoons each) to a soft consistency (my peanut butter must be thicker than most, because that is way to stiff for me), slaked for 3 mins, and then spooned into a mosaic baggie and tied it off.  One batch was used by a friend to mosaic onto (sealed) sandstone, and the 2nd batch was used by me on sealed MDF.  I worked until 7:30pm, and stopped to prepare dinner (my friend went home with her still useable baggie in hand at 4:30pm).  I watched the idiot box till 11:30pm, then went to clean up my piece before bed. I realised the adhesive in the baggie was still malleable, so finished off the shards I was using for the sea. The adhesive was still fully workable at 11:30pm – a full 9 hours after mixing!

Because the adhesive was so creamy I was able to cut a smaller hole. No bag explosions! This was great for me, as part-way through my piece, I realised I wanted to use shards for the sea underneath the boat. Using the softer mix, with a smaller hole, I was able to do so!

Outcomes

a) I now recommend water only as the mix;
b) no more fingers coated with adhesive goop!
c) I am now in love with Cement-based adhesive, and my Mosaic Baggies – a marriage made in Heaven!
d) the Additive is available for use in conjunction with our Cement Adhesive when working in demanding mosaic installations, including 3D, special effects, mixed media or heavy traffic areas. Use with the trowel method of application.

Just a note on Terminology:

There are a number of terms used in the building trade, and they are often confused:

• Slake Time (3 minutes): The amount of time you should let a mosaic sit before using it.  It’s important to allow this time to pass so the chemicals in the ingredients can bond and strengthen. 
• Open (Working) Time (25 minutes at 23ºC): The amount of time after applying the adhesive to a surface where it can still bond with another material before it starts to set.  The product starts to skin over and becomes less adhesive. Also important to note that handling the product with ungloved hands can adversely impact this.
• Pot (Usable) Life (90-120 mins): The amount of time a mixed adhesive remains workable after being mixed.  I find the product stays usable for a much longer when used with my Mosaic Baggies, due to the fact that they create a sealed container, and the product is air-cured.
• Curing Time: the time that determines how long things take to fully cure.  A series of chemical reactions occur during cure time. These chemical reactions allow things to set, harden and develop traits. Cement products may continue to cure for weeks, months or years. Many factors have an impact on the curing time of a product.
  • Leave for 24 hours (at 23ºC) before grouting.
  • Do not submerge for at least 2 days after application
  • Leave for at least 7 days if using outdoors ungrouted (for example with Smalti).

Questions

Comment: Yesterday I used the adhesive just with water in a home made baggie and it was still squishy 6 hours later so I used it up – another hour’s worth.
Question:  I find using CBA that tess drop off with the tiniest bump. Am I doing something wrong ?
Answer: No – it doesn’t seem to adhere, until it does. Once you have your tesserae set in position, don’t touch, move or bump them. The next day, they will be stuck like a rock. Full cure is not achieved for 24 hours. Before this, tiles may appear not to be sticking – but they definitely do. If you have to move them, scrape off old adhesive and re-apply.

This can work to your advantage once you know.

• Don’t worry about cleaning off fresh adhesive – it will only smear everywhere.
• Leave it until dry, but not set. Then you can clean off the edges with a spudger, or tool of your choice.
• This means that the next day you have a clean edge to continue on with your work.
• Also, don’t be tempted to smooth it out with your fingers (as I have seen some do). The oils from your fingers may impact the bond (a gloved hand is OK is smoothing over large areas of a substrate).

Question: How long does CBA last after opening and does it have special storage requirements?
Answer: Brands MAY differ, but generally, CBA has a 12-18 month shelf life and is best stored dry in sealed containers. Avoid damp conditions, and if possible, store up off the floor. My product comes double bagged, for ease of shipping. Cement products are hydroscopic, and as such absorb moisture from their surrounds (even cured concrete).

Enjoy! And do a price comparison between my adhesive and others… no additive required with mine! As an Australian product, my CBA does not incur the high shipping costs of imported products. How good is that? I do love to support Australian manufacturers!

Adhesive: https://merlinmosaica.com/…/merlin-mosaica-cement…/
Mosaic Baggies: https://merlinmosaica.com/product/mosaic-adhesive-kit/