Most manufacturers of acrylic sealers recommend re-sealing stamped concrete with the identical product that was used originally for concerns of incompatibility or weakened bond strength.
As residents of one of thirteen states in the U.S.A. with recently increased chemical restrictions, nearly all of the sealers used prior to 2005 are now outlawed and we are forced to find alternatives to use for re-sealing older stamped concrete projects. Because of this legal change, we have worked hard to find a user-friendly, good-performing sealer for exterior decorative concrete, i.e. SDI Stamp Seal – Klear Gloss # 2. We firmly believe that this is the single best NJ VOC compliant formulation available. With that, we have worked specifically on making sure that our Klear Gloss # 2 will work compatibly with our original formulation (SDI Stamp Seal – Klear Gloss), and our penetrating version (SDI Stamp Seal – Penetrating).
For your stamped concrete projects that you know have been sealed last with something other than one of our Stamp Seal formulas, please contact us or the manufacturer of the product last used (if used successfully). It will likely be recommended that you first test a small area and allow it to weather for a while. If the new and old sealers do not bond to each other with enough strength or if they are not bonded strongly to the concrete, that bond will be compromised under the pressure of moisture, sun, and time, resulting, sometimes, in a whitened film.
Evidence of a problem is most likely to develop within a month but will occasionally take longer to identify itself so please allow enough time to pass for your test results. There is still no agreed reason between chemists and authorities as to why this occurs but the consensus is that it is related to film thickness and moisture vapor pressure, which is why most problems arise shortly after, or during, periods of excessive precipitation. It is also debated whether or not there is, in fact, an identifiable compatibility issue between different acrylic sealers with different resins and different chemistry. There has been no definitive testing that suggests there is a specific incompatibility that results in consistent failure or delamination of any one acrylic sealer when used with any particular other. However, it is FAR more rare to see a sealer failure occur with the exclusive use of a single product applied in very thin coats. This seems to hold true for re-sealing as well, as long as the surface is clean and very dry before the re-seal coat is applied (again, very thinly).
We now understand that changing products too often can only increase the likelihood of problems arising if re-sealing with a new sealer. Sealant Depot, Inc. acknowledges that we have changed suppliers frequently in the past in search of the best product for your application based on performance, ease of application, and cost as well as forced changes due to legal constraints. We believed that we had found a superior sealer formulation with the SDI Stamp Seal – Klear Gloss late in 2004. However, we were only able to stock a limited supply of that formula before the V.O.C. restrictions were increased , making it, and nearly all other solvent-based acrylic sealers illegal in NJ as well as an additional 12 other states in the U.S. (most of the Northeastern states and California). That legal change required us to search further for yet another formulation. Using the same resin system as in our original Klear Gloss, Klear Gloss # 2 was developed and is compatible for use with its predecessor, keeping in mind proper application rates and conditions of the substrate and environment during its curing stage. That is not to say that it is compatible with all sealers nor in all circumstances.
For a better grasp of how sealers may work together, it is important to know the product you are re-sealing over. With some help from your supplier or manufacturer, and a light education in general sealer chemistry, most concerns of incompatibility can be reduced. If you have questions about the chemistry of a product that has been used in the past and you would like to re-seal it, please contact Sealant Depot, Inc. or the product’s manufacturer. If the original product is not readily available and/or you would like to use a different product to re-seal with, not all hope is lost. It is best to use the most similar product available to you (use like resins, do not mix different resins i.e. styrene acrylics, methyl methacrylates, or pure acrylics) and perform a reasonable-sized test area (one that is large enough to yield true results, and also small enough that it can still be stripped if necessary).