What is a "Halo Ring?" It's a renderers nightmare that's what it is!
Halo rings in render are formed during the scraping process when an applicator unwittingly scrapes through the finish coat to the much harder base coat or first pass resulting in a flat textured area that cannot be matched into the rest of the wall. The worst cases may even go as far to reveal the mesh embedded into the first pass as the below picture shows:
Can they be avoided?
Most renderers I speak to have a story about a halo ring in either K Rend, Parex or other manufacturers mineral renders that caused them real headaches. Whilst we have had some success in correcting them with our Mendrend Render Repair System we cannot guarantee success under all circumstances as they all tend to be different. This is one of the most common issues we are asked to look at and if I'm honest the one we struggle with the most so if we can provide guidance to avoid it in the first place it suits us!
- Before starting application check the walls with a long straight edge. If any bows or bellies over 3-4mm are present in the substrate then seriously consider the use of a K Rend or Parex base coat instead of just priming to level the walls out ready for the finish coat.
- If applying a base coat ensure this too is level with a straight edge before applying the finish coat. Ensure that the K Rend or Parex finish coat is applied to a depth of at least 12mm over the top of the base coat to allow 2mm to be scraped with little risk of scraping too much away.
- If you aren't applying over a base coat and instead applying the finish coat in two passes, do not apply the first pass too thick, we advise the first pass should be around 6mm maximum and level for both K Rend and Parex. The second pass should be at least a further 12mm on top of that applied wet on wet.
- It is common for suppliers to under estimate the amount of material you will need in an effort to look like they are the cheapest or doing you a favour. They know that you will be straight back on the phone if you are running out of material and trying to get a job done. What generally happens instead is that the inexperienced applicator starts to take risks by spreading thinner. Always ask your supplier to justify the quantities quoted, backed by a manufacturers specification document. It's always better and cheaper to have a few bags left over at the end of the job rather than running out of material. Always ensure you allow 5-10% additional material for wastage on top of manufacturers quoted consumption figures as that doesn't tend to be included. You'll figure out how much you will need to allow for this yourself once you get a feel for the material after using it for a while.
- Every applicator uses a slightly different amount of material to the next due to differing working patterns. Keep a record of material consumption over a few jobs to see if you get consumption rates that suit you.
Avoiding this issue is as simple as that! Hopefully you find this of help and avoid the renderers curse in future!