added process pics

docs/files/recipes/phmodifiers.md

@@ -110,6 +110,13 @@ Four PH modifying solutions of approx. 170 ml each (PH 1-2, PH 5-6 acidic, and P
 
 ![](../../images/phpaper9.jpg)*Cutting tear-off strips, Loes Bogers, 2020*
 
+![](../../images/phmodifiers1.jpg)*Soda ash and citric acid, Loes Bogers, 2020*
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+![](../../images/phmodifiers3.jpg)*Preparing the acidic modifiers with citric acid, Loes Bogers, 2020*
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+![](../../images/phmodifiers2.jpg)*Modifying until you get the right PH values, top to bottom: citric acid 2g, citric acid 0.1g, tap water, soda 0.1g, soda 2.0g, Loes Bogers, 2020*
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+
 ## Variations on this recipe
 
 - Make a better design for the booklet, without wasting material.