Blu-tack can pull the paint and even the wallpaper off the walls. It can also leave grease marks and in some cases the tack dries so hard, it can’t easily be removed without causing some damage. You don’t want a deduction from your deposit for redecoration at the end of the tenancy because of the damage removing the blu-tack has caused.
Remember it is your responsibility to return the property in the same condition it was in at the start of the tenancy, as recorded in the check in inventory. Please note that although reasonable wear and tear cannot be deducted from your deposit, blu-tack marks do not count as reasonable wear and tear.

‘White-tack’ may seem like an alternative, but you should still avoid using this as it can also leave grease marks.
Following these simple steps can help to avoid a deposit deduction at the end of your tenancy.

TOP TIP There are now products on the market claiming they can be used without leaving marks, but we recommend you ask for permission to use these from your landlord/agent in writing. Then make sure you test the product before using all over the walls and read the instructions properly on how to remove them.
Moving into a new property can be very exciting, and you will want to make it feel like home by putting up posters
or pictures. Using blu-tack can seem like the best and easiest option.
However, the likelihood is that your tenancy agreement will contain a clause banning you from putting holes in walls
or using blu-tack due to the damage it leaves behind when it’s removed.

From a Tenancy Deposit Protection Guide published by Tenancy Deposits (NI) Limited