Remove red brick dust from new render

neilmcl

Just had the house rendered and when getting my alarm box refitted, on a rather windy day, red brick dust blew onto the white render whilst drilling the fixing holes, staining it in the process. I've tried hosing it down but it's still there. Any ideas on the best way to clean it off?

flashg67

a hydrochloric acid based cleaner may be the only option if the fine dust has penetrated the 'pores' on the render