As the sub-heading suggests, 3C Paintable is not just a standard caulk but rather, a premium acrylic sealant that out-performs all generic caulk products on the market! With standard caulks often cracking, breaking down and/or shrinking in the joints, call backs and snagging for tradespersons take extra time and costs them money, as does the trouble of re-applications for DIY users, so to avoid the problematic negatives of the budget products, the extra cost is more than justified for the superior quality.
3C Paintable is registered as ISO9046 permissible movement capability. Movement is fully tested to determine how flexible the finished product will be with various substrates when adhered to 2 x sides. This accomodates movement in building structures etc. The higher degree of movement, the better the performance. Paintable's incredible 18% movement makes it suitable for use on large joint movements in substrates ranging from masonry, concrete and timber to plasterboard and UPVC etc.
We don't like to make false claims on our products, so suffice to say that the short answer to this question is no, an anti-mould fungicide additive is absolutely necessary! For applications such as around baths, sinks and shower trays you should be using a dedicated sanitary silicone sealant such as 3C HM.
Saying that, if the gap or crack to seal or fill is in an area where perfect ventilation exists, then possibly 3C Paintable can be used to get you out of trouble so long as it's not going to get continuously wet and not be able to dry.
Although we market 3C Paintable as being a filler as well as a caulk, it's important to realise that the more flexible a product is then the more rubbery the consistency will be when it's fully cured. This means that in the traditional sense, when tradespersons or DIY users apply caulks or 1-part fillers, whether it's a paste in a tin or an acrylic, water-based sealant type in a cartridge, they tend to expect a certain kind of texture and finish that makes the material easy to sand down and shape etc. (i.e. it looks rigid and feels quite hard to the touch) Thus when applying the product, they would purposefully leave it proud of the joint, gap or crack. With this fact in mind, we suggest that, yes, Paintable can be used as a filler BUT only if you're not planning to sand it back and/or shape it to a finish! To give you an example, if you're overfilling a screw hole and letting it cure with a view to sanding it down then over painting it, then 3C Paintable isn't recommended! Instead you should consider 3C Decor Caulk.