On-site sample panels are the most reliable way to select a pointing mortar, because colour, texture, and performance only become clear once the mortar is mixed with your specific sand and applied to your specific masonry. The goal is to prepare a small range of lime mortar candidates, apply them to concealed or test areas of the actual wall, and let them cure so you can compare them against the existing mortar and the surrounding stone or brick.

Before we arrive to prepare samples, you need a clean, raked-back area ready to point. Choose a discreet location on the building, ideally under eaves or in a sheltered spot where the existing mortar is sound and can serve as a reference. Avoid areas that will remain visible if a sample is approved.
Remove the old mortar to a depth of at least 2.5 times the joint width (or a minimum of 25mm) to give the new mortar a proper key. Take care not to damage the arrises of the masonry. Clean out all dust and debris.

We will then thoroughly dampen the raked joints to control suction. This prevents the mortar from drying out too fast and losing strength. Prepare three to six different mixes for comparison.

These will vary in:
- **Binder type:** For example, a non-hydraulic lime putty versus a natural hydraulic lime (NHL).
- **Mix ratio:** A standard starting point is 1 part lime to 2 or 3 parts sand (1:3), 
- **Sand/aggregate:** The sand dictates the final colour and texture. Test locally sourced sands or graded materials to match the original.

We will mix and apply the Samples

Lime mortars behave differently from cement, so mixing and application technique matters for a fair test. We will measure the samples by volume. For lime putty, we generally do not add extra water—the putty provides the moisture. We will apply to the wall using a pointing iron, push the mortar firmly into the joints in layers (about 25mm at a time), ensuring it fills the back of the joint completely, and finish using different techniques. 

Once the mortar has stiffened to a leathery consistency (hard to dent with a thumb but markable with a thumbnail), we will finish it. Cover the samples and protect them from direct sun, wind, rain, and frost. You may need to mist lightly in warm weather to keep the mortar damp as it carbonates once we leave the site. Non-hydraulic limes need the most careful curing.

Do not proceed** with the full repointing job until the sample areas have been inspected and **approved in writing** by the relevant authority or client. Keep one approved sample panel protected on site as a reference benchmark for the rest of the work.

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