[Solved ]Assigning material always create new instance...

Hello, I've got a weird problem with materials :/ So I'm instacing prefab and then I want to assign material which is stored in List in ScriptableObject but to prevent instacing new ones I thought storing material from one object in new List would prevent it from creating new instances but it doesn't work... Every single object have different material instance
Maybe there is something I'm missing :/

Code (CSharp):

1. var mat = GameplayUIManager.FurnitureDataContainer.FurnitureList[f.ContainerID].MaterialOptions[f.FurnitureObjData.UsedMaterial];
2. var MaterialInstances = BuildingManager.Instance.MatInstNames;
3.  
4. if (!MaterialInstances.Contains(mat.name))
5. {
6.     var r = f.GetRenderers();
7.     for (int i = 0; i < r.Count; i++)
8.     {
9.         if (i == 0)
10.         {
11.             r[0].sharedMaterial = mat;
12.             MaterialInstances.Add(mat.name);
13.             Instance.MatInstaces.Add(r[0].sharedMaterial);
14.  
15.             mat = Instance.MatInstaces[MaterialInstances.FindIndex(x => x == mat.name)];
16.         }
17.         else
18.             r[i].sharedMaterial = mat;
19.     }
20. }
21. else
22. {
23.     mat = Instance.MatInstaces[MaterialInstances.FindIndex(x => x == mat.name)];
24.  
25.     var r = f.GetRenderers();
26.     for (int i = 0; i < r.Count; i++)
27.         r[i].sharedMaterial = mat;
28. }
29.  

 

Problem solved.
The problem was that in other script I used "material" instead of "sharedMaterial" which caused new instance to pop up